Factors
I had an old Sears/Kenmore carpet cleaner based on a wet/dry vac and it was monstrously heavy and noisy. It did not have rotating brushes, but did remove dirt fairly well. When the water pump broke, I needed something else. The Amazon reviews for the Hoover models are better than any of the Bissells, but upon closer inspection there are a substantial number of Hoover owners who report shearing off the brush plastic drive-shaft after only a few uses. This is a $30 replacement! Consumer Reports (Oct 2010) says that all the larger Hoover and Bisssell cleaners clean equally well, but that Bissell models are somewhat quieter. They also report that Bissell vacuums are more reliable than Hoover (and I suppose carpet cleaners will be similar). Furthermore, Bissell has a 2 year warranty and Hoover has a one year warranty (although in some Amazon reviews, Hoover owners report only a 90 day warranty!). The Bissell Lift-off Deep Cleaner model 27F6 (red) was on sale at Target so I took a chance it would clean OK and be reliable.
NOTE: Bissell lists 4 model numbers for this unit (94Y2, 27F6,35K3 and 73H5). They appear to differ mostly in the attachments included. The Amazon model is 94Y2, but it appears identical to 27F6 except is green, but it does NOT appear to include the "deep reach tool" I so love (see below)!
The Manual
You would think that for the $$$$ I spent Bissell could have included a good manual, but no. The manual is spartan with murky illustrations. It took me longer than I would care to admit to figure out where to put in the 4 screws to assemble it. There are seemingly 4 obvious holes for the screws, but these are not correct. The actual holes are somewhat hidden even though they are "marked" with almost invisible arrows. The cleaner disassembles cleverly for cleaning and storage, but it is a challenge to figure out how to do this from the manual illustrations. The quick start guide has color pictures, but they are tiny, tiny. Larger more detailed color pictures would be very desirable. Come on - how expensive could this be?
The Lift-off Portable Cleaner
The unit is made so the carpet cleaner section easily lifts off the base (by pressing a pedal) to convert into a portable spot cleaner. I thought that this was just a gimmick, but I was wrong! It is the best part of the Bissell cleaner. The lift off cleaner with its 6 ft flexible hose fits PERFECTLY ON STAIR TREADS and it is light and easy to move. THIS IS GREAT! Start at the top of the stairs and slowly work your way down a stair at a time using the included "deep reach tool" (may not be included in the Amazon unit). Remember to keep the tool pressed firmly against the rug when releasing cleaning solution or it will spray all over your pants!! The results on my hard to clean carpeted stairs with somewhat matted carpeting were remarkably good. The "deep reach tool" has a brush plus hard plastic prongs to dig into matted carpet and raise the pile. I'll admit that I only did the matted down parts of the stairs, and now these formerly dirty parts have a noticeably higher pile (about 1/4 inch)! It looks almost new (almost) and the result has so far lasted a day with light traffic. So I now may have to do the rest of the stairs so that the "clean" parts will look as good as the formerly matted parts. The "deep reach tool" itself is not easy to clean out.
UPDATE 11/8/11: Stair treads still look good after 1 week. The carpet has not yet returned to its formerly crushed/matted state after 1 week of use.
Water Removal
Water removal really depends on the carpet type. Deep pile carpets retain more water than others. With a ceiling fan my deep pile carpets took 2-3 hours to dry, but in areas without the fan the carpets took 8-10 hours. I can't blame Bissell since even a potent high hp wet/dry vac was not able to get out any more water. It is not clearly indicated in the manual, but the Bissell has a overflow preventer that shuts off the vacuum suction if the dirty water level becomes too high or if the cleaning solution is empty (or close to empty - kind of annoying). If so, you will have to correct the problem and then turn the vacuum on again. All carpet cleaners (especially rentals) dribble a bit of cleaning solution (from solution left in the tubing) when shut off. The Bissell is somewhat better in this regard.
Carpet Cleaning
Consumer Reports says that all the larger Hoover and Bisssell cleaners clean equally well and I am satisfied with the results from the Bissell. If my carpets were dirtier, the results would have been more dramatic, but the dirty water was indeed dirty. Some carpet cleaners have one water tank for the dirty water with the clean water placed in a bladder located inside the dirty water tank. The Bissell Lift-off Deep Cleaner has two removable tanks which I think is better. The dirty water tank is easy to remove and dump. The clean/soapy water tank is easy to fill (although harder to dry out for storage) and contains 3 quarts (6 lbs). I did not use the included bottle of Bissell cleaner solution since I used up an older bottle of carpet cleaner I had sitting around (it seemed to work well). The tanks have to be emptied often, but if Bissell had made these tanks bigger then the unit would (of course) weigh more and be harder to move. I feel the current size is a good compromise.
Cleaning Solution Usage
You will go through the cleaner solution in a hurry! Some people are concerned about the amount of solution a carpet cleaner uses. Actually, more is better. Remember that a small amount of water will always remain on the carpet (no matter how good the carpet cleaner is). Now look at your dirty water tank - some of THAT muddy water is remaining on the carpet! The more solution that is used in cleaning, the more dilute the dirty water should become, and thus less dirt will remain on the carpet. Also keep in mind that the slower you go (and the more thoroughly the cleaner cleans) the more cleaning solution will be used. People who report they only use a little solution are probably going too fast. When your carpets are relatively clean, you can go faster and use less solution. If you are worried about cost, just use a cheaper carpet cleaner solution (they probably work all the same anyway). Bissell recommends 2 oz of their 2X concentrated cleaning solution per tank.
Rinse Cycle
Many carpet cleaner models from Hoover and Bissell have a switch to change from cleaning to rinse. The Bissell Lift-off Deep Cleaner does not have this so if you want to rinse you will have to clean the carpet first and then change to water to rinse the carpet. Doing so will probably be faster than to rinse after every pass anyway. Bissell does not recommend rinsing. Also consider that most modern cleaning solutions contain ingredients designed to protect the carpet that you may not wish to rinse off (such as ScotchGuard protection). When used as directed and after the carpet is dry it is impossible to tell if you have rinsed (no discernible residue). I don't rinse.
Weight is NOT a problem
Some other Amazon reviewers here have suggested that this Bissell is heavy. No. I would say instead that it is very light! Here's why. All Hoover and Bissell cleaners are fairly heavy/bulky and difficult to carry. This cleaner is very easy to move because you merely lift off the portable cleaner from the base. Now you have two easy to carry parts (base = 12 lbs; portable cleaner = 13.5 lbs). Carry the base and portable cleaner separately upstairs, then press to click back together (make sure both sides click) and fill the tank with cleaning solution (6 lbs). Easy!
Fiber Bunnies (balls)
All carpet cleaners (both Bissell and Hoover) with active spinning brushes liberate a few fibers from your carpet and roll them into fiber balls. Assuming you don't clean your carpets daily, this should not contribute to carpet wear. Be aware that the rotating brushes on your vacuum cleaner also do the same, but you never see the bunnies because the vacuum cleaner immediately picks them up. Carpet cleaners have a vacuum slit too small to pick up the bunnies so you will see them scattered over the floor. If this will greatly distress you, do not get get a cleaner with rotating brushes (but of course the rotating brushes improve cleaning performance).
Durability and Maintenance
To be determined. As mentioned above, the cleaner disassembles cleverly for cleaning and storage, but the "deep reach tool" does not seem easy to clean out. I will try to update.
Etc.
Another reviewer here got her unit through Amazon's Vine program. You may notice that I am also sometimes a Vine reviewer, but I bought this unit ($$$$) and this review is not a part of the Vine program. As the other reviewer explained, Amazon does not pressure Vine reviewers to write good reviews.