I'd been thinking of getting a sim for some time and finally took the plunge on this one, which is certainly the least expensive one available. There's plenty of info on this on the internet so I won't go much into it, but I've been quite satisfied so far. Occasionally it won't pick up your swing (maybe once every 20-25 swings) and you have to reswing. Of course that only happens when you've really hit one flush. Distances with clubs weren't particularly accurate for me and this seems to be something that is fairly common, but you can adjust the distances (e.g. increase distance 10%, decrease distance 5%, etc.) to make the sim distances align with your real ones. I was consistently hitting drives of 320+ which felt good but wasn't going to do my real game any good. Incidentally, my average driving distance is more like 265, so I had to decrease driving distance about 17%. Programming in my clubs and setting distances took maybe 30 minutes and was sort of fun anyway.
There are several courses that come with the sim, as well as a driving range that you have to download as an update once everything's installed. There were several updates to download and while they're not necessary to start playing, if you want the newest courses and the range they are, and they take a couple of hours to download. You can play it right out of the box but download the updates overnight.
I was somewhat dismissive of the computing power recommended for this program. My computer is not quite 2 years old and certainly fits the minimum requirements for running the software, but running the program is not smooth. I've turned off everything in the program that takes processing power but it's still not great, though acceptable, and this isn't really DD's fault anyway, but just the way it is with software and computers. But the newer and more powerful your computer the better this will look, and it does make a difference.
Some people have complained that swings with their driver don't register well with the system. Can't say I've had that problem. So far all of my clubs have been picked up by the sensors just fine. One thing that DD has apparently changed though is the measurement of swing path. For example, after a swing you'll get a reading that says something like, "Clubface open 2 degrees, swing path inside out." Sometimes the swing path will be "very" inside out or outside in. Based on screen shots on the DD website, the reading used to give degrees of inside out or outside in. I've sent some emails to DD trying to find out how inside out "inside out" is, i.e. at what degree of inside out does a reading become "very inside out," but I've gotten no response. I suspect it's pretty significant however, based on some testing on my own, so this wasn't that big a deal. If you get "very outside in" it's either a dead pull or a banana into the next fairway. Any swing path less severe than that is likely to turn out okay based on my experience with "carryover" onto the real range after hitting on the sim.
I've also seen some complaints about lighting having to be perfect to get accurate readings. I haven't had that problem either. I have it in a large front room with just a lamp on and it works fine. No problems with shadows, needing overhead fluorescent light, etc. The foam balls they give you do bounce off stuff. I bought a $30 net from Izzo to catch them and it works great. Finally, the device itself sits 1.5 inches off the ground. They sell a mat on the DD site but it's as expensive as the device itself. I had some spare carpet that was 1/2 inch and just folded it over three times and it works fine. But be aware that you'll need something to stand on when you hit.
I really think this is an excellent product. I didn't give it five stars because it wasn't perfect, but for much of an improvement over it you have to spend $700 more, and for the best sims around you will drop tens of thousands of dollars. If money's no object get a custom job and drop the $50K. If you just want to be able to hit balls when it rains and have some idea what your swing is doing, this is your huckleberry.
UPDATE: I mentioned above that computing power was playing a big role in the choppiness of the sim. That's true, but not as much as I thought. Once I removed Vista from my machine and put XP on instead, the smoothness of the sim increased dramatically. Faster computers will still work better, I'm sure, but in this case the problem seemed to be that Vista sucks, not that a brand new computer is required to run DD.