Yeah, I've used them in the past, and they're the only way to do this kind of work.
They're not too difficult to manage, but make sure you go over the floor beforehand with a hammer and punch and drive all nails a few mil below the surface of the wood. These will shred the sandpaper, and the less of this you use, the less you pay in the end. Most places will give you more than enough sheets, and refund you on whatever you bring back unused. Get both a drum sander for the main body of work, and an disk sander for doing around the edges.
Don't even bother with the hand sander, especially if the floors are in a bad way as you say.
Leo