First off, let me say that the customer service of the company is outstanding. They really seem to believe in composting and want to help you make great compost (as opposed to just selling you a product). When I've had issues in the past and contacted them, they've promptly sent out free replacement parts. When they saw my poor composting experience, they contacted me and offered to ship out a new unit free of charge (and any assistance in setting it up). If you read the other reviews, it seems like they frequently do this with other customers as well.
Having said that, I'm still not sure I'd recommend it. At best it's a recommendation with caveats provided the person is willing to deal with its shortcomings. Does it work? Yes. I've made several batches of compost with it. So what's the problem?
Please keep in mind that I'm an apartment dweller (largish one bedroom), so the review is biased in that direction. Also, since it's marketed as an indoor composter, I feel that the points below are entirely justified. I've also updated the review below to reflect the supposed improvements they've made.
Lets get the positives out of the way:
* Fast - Naturemill's composter will make compost much faster than the backyard types (even in warm weather, not to mention places that have winters - unless you vermipost with worms inside). You also don't have to worry about keeping worms alive should you take an extended trip somewhere or have that on your conscience if the worms don't make it). =)
* You can supposedly decompose meats and pet feces that you couldn't with other methods (though I haven't tried it - and wouldn't since it has to reside in the apartment).
* Makes great compost when all is well.
Negatives:
* Noise - While not mixing, there's a slight hum from the air pump. It's somewhat annoying, but nothing too egregious. It's easily audible though, and because there's less ambient noise at night, the unit will seem louder. However, while it's mixing, the motor whines loudly. As the mixing arm brushes pass the metal tabs, it makes repeated loud clicking noises (they seemed to have lessened this somewhat, but it's still noisy). It does this every four hours, so it'll make a pretty good amount of noise at least twice during the night. If someone crashes on your couch for the night, it'll definitely wake them.
* Smell - If you keep the lid closed, it manages to pretty much keep the smell inside (with the help of an activated carbon filter). Mind you that I'm not wimpy about smells, but the minute you open it, well, it smells like you've brought a composter inside your apartment. To be fair, what did you expect? It's composting, so it's going to smell like one. When it's working properly, it still smells like earthy, musty compost. Doesn't bother me, but my gf won't go near the thing and always begs me to not open it. Eventually you learn to not to open it (within a couple of hours) before guests come over or before you cook or eat. Hint: I've found that using copious amounts of coffee grounds (gathered from work) significantly helps with the composting smell. Just note that even though it's listed as a "brown" item, you'll still want to add an additional carbon source to balance out the nitrogen in the coffee grounds. Hint: Starbucks gives away free grounds for composting (google "starbuck composting").
* Inconvenience - The manual says to not use paper (like from a shredder) and to use sawdust/pellets instead. I don't know about you, but I don't have a steady supply of sawdust. It's silly to keep buying sawdust pellets (from them) just to make compost. They say you can ask your local lumber yard for free sawdust, but there's no way to know if the sawdust there contains cuttings from plywood or particle board (glues and chemicals). As mentioned on their website, you can also buy "wood pellet fuel" from your local Home Depot like places. Even though it's not expensive, the minimum size is 40 lbs (not great to find storage for it when you live in an apartment).
* Leaks - Note that it comes with a thin plastic tray that goes below the entire composter to catch excess liquids (see manual). Just make sure that you keep an eye on the tray so that it doesn't overflow. It's mostly just excess moisture from the food, but be warned. Also, from the manual: "Select a flat and level location. Unit will not work properly at a tilt of more than a 1 degree." In case you're wondering, a one degree tilt is nothing. It's nothing you'd ever notice, even if I gave you a leveler to measure it. They should simply design it in such a way that it can tolerate being slightly off. It's hard to draw a parallel, but imagine if your fridge leaked unless it was perfectly leveled. Also, they warn you to not place the composter on any surface that can be ruined by liquids overflowing the tray ("Do not use on carpet or wood or other unsealed floor materials, as damage to floor may result."). Additionally, you'll find that water pretty much collects all over the "curing" compartment. Only small amount of liquids make it inside the drip-tray. I think the problem stems from all of the internal surfaces being the same temperature, so that the water vapors doesn't preferentially collect somewhere and drip into the drip tray. So until they can incorporate some colder vapor condensing surfaces that can guide the water into the drip-tray, you'll end up with extraneous water all over the internal bottom compartment (with excessive moisture leading to mold issues).
* Mold - As the other reviewer stated, I've also had a mold problem with my composter. If you're going to use the compost for indoor plants, throw it out unless you want to spread mold to your plants. Have fun scrubbing.
* Unstable - The unit isn't heavy enough on its own, so you'll have to hold the unit steady with your hands while stepping on the foot pedal to open the lid. Yes, it's easier to simply just open the lid with your hands.
* Cost - I don't think I have to elaborate much here. If you have a backyard, you should check with your city because many subsidize the cost of backyard composters.
All in all, this is an expensive and fussy way to make compost when it's going well (if the green/brown/moisture balance is off, it can smell a whole lot worse). A friend saw mine and asked me how well it worked and if I'd recommend it. I just couldn't recommend it to her. I think it's a great idea, but the execution still has issues.
For more details, you can also google "NatureMill PRO XE Gizmodo review" and see a few photos of the unit in action (hint: they don't recommend it either).