The Kenmore Progressive vacuum so far is the best vacuum cleaner I've ever owned.  This is in comparison to Dirt Devil, Hoover, and Eureka uprights.  I've had it over two years now and it still cleans just as well as it did when I first bought it.  It's never required any maintenance aside from removing hair from the main rotating brush.  It picks up most debris on the first pass and gives professional looking results.  I especially like the dirt sensor feature.

On the down side, it is a somewhat bulky machine, but the attachments allow reach into smaller spaces.  It is a little annoying...