Well, I went ahead and decided to refinish my hardwood floors myself. The estimate came in at $2600, way way way over our budget, and the other two companies were booked for the next three weeks, which is about when I need to be out of my current place so that doesn't jive.
I rented the drum sander and did the majority of the sanding yesterday. Not too hard. Just tedious. Have to go very slow, but the 20 grit sand paper chewed right through the old finish, and paint, and old glue in some spots with no problem. A lot of things I've read mentioned using a combination of 40, 80, and 100 grit paper, or 60, 80, 120. But the guy at the shop recommended 20, 36, 80, and only going up to 120 if I wasn't going to polyurethane. Worked like a charm.
I rented the edging sander today and that thing kicked my ass. Bent over or on my hands and knees all day. The thing is constantly trying to get away from you, like a floor buffer, it's tough to keep in under control. It took longer to do the edging than the rest of the floors.
I had to buy a separate sander (a Mouse) specifically for getting in the corners and around door jambs, and parts of the steps the edger wouldn't reach. Also bought the stain and poly today.
Drum sander and paper - $120
Edge sander and paper - $65
Mouse sander and paper - $45
Pre-stain conditioner - $60
Stain - $60
Polyurethane - $75
Misc. Items (brushes, rags etc...) - $50
Total - $475. Throw in enough Advil for a football team to cure my back ache, call it about $500. Saving $2100 doing it myself. It'll probably take all together a couple extra days than what the pros said it would take them (three days). Well see what the finished product looks like in few days. I'll post some before and after pics.