I used the U-Sand from Home Depot for my whole floor, no drum sander or edger. It was very slow, but it left the floor perfectly flat and there were no signs of transitions or unevenness. It also got right up to the edges. I was very very happy with the finished results. If you go that way, you'll probably want to use 80 grit to get the 60 grit marks out. Then hit it again with the 100 or a 120. The U-Sand takes off so very little material each pass that you'll be there forever trying to get the 60 grit marks out with 100 grit. Also you'll never blend anything with a 100 grit and the U-Sand. If you want to blend out your edger marks and other areas, definitely use the 80 grit. Don't go fast with those things either, otherwise you'll be disappointed. If you're bored out of your mind while sanding with the U-Sand, you're probably doing it right.
Here's my floor I just finished on Sunday. U-Sand 40-80-120, then sealed w/ Last n Last 100S, then screened with Clarke square buff with 150, then poly'ed w/ Last n Last 1500 satin, then screened again with 180, then final coat.
http://i1168.photobucket.com/albums/r48 ... 064739.jpghttp://i1168.photobucket.com/albums/r48 ... 064634.jpg