I've been running Vista on my home desktop and my wife's Dell XPS m140 laptop since it went RTM, and I've got nothing but nice things to say about it.  However, I can't run Aero on my wife's laptop.  Turns out that Intel has elected not to make the prerequisite WDDM video drivers for the 915GM chipset in the XPS m140 and half of all the other laptops manufactured in 2006.  They blame Microsoft, but honestly, I just don't care.  I bought a "Vista Ready" PC in 2006, and the damn thing isn't completely Vista ready.  Jerks.