I always use an Oreck. I like them because they are very, very light, VERY powerful, and have the longest lead ever - so I can do all my upstairs in one go.
The downside is you have to buy the bags by mail order and they are quite pricey. You can replace the roller and belt yourself very easily if you ever need to. I did break one but that's because I'm not very careful about picking up hairpins and things and suffered a bit of a meltdown once.
I like them so much I wouldn't ever change brands - except I am getting a cheap Roomba-clone for Xmas following some recommendations on here.