The prices are horrifying, but I agree that you don't want to go too cheap. I've run on cheap treadmills, and it's not a good experience. The one I have at home is a Pacemaster Pro Plus HR, and I've had no trouble. I paid around $1800 for it a few years ago, but I use it all the time and consider it to be a great investment for me. It has good stability, which is something I really wanted in a home treadmill. It has heat rate monitoring and incline as well as the usual bells and whistles (like programmed workouts). www.runnersworld.com
reviews home treadmills, so that might be a good place for you to look for more info. Home treadmills seem to run from $400 to $5000+ . When you determine what you're willing to spend, your best bet is to go to retailers and go for a walk/run on them to see which ones feel good. When I bought mine, I went to several stores and went for runs on several models. In the end, the one I bought was not the most expensive one I tried but the one that felt good for the money.
p.s. When you do find a treadmill, buy a good fan to blow on you while you're exercising - it makes the experience much more pleasant.