My wife and I have been lucky enough to stay in some of the best hotels Vegas has to offer. This was our first time at the Vdara and we enjoyed it. We have stayed in the City Center twice before (Mandarin Oriental and Aria) so we knew the turf.
The main difference in this hotel compared with the other 4/5 star hotels on the strip is lack of casino and no real restaurant on property. No biggie-the Aria, Bellagio and Cosmopolitan are within walking distance have have top notch restaurants and of course casino's. Vdara is also completely non-smoking (huge plus).
Staff was nice, friendly and helpful and the room (standard 34th floor facing the mountains) was very nice and new. All rooms seem to have some sort of kitchen/kitchenette, although the only city I generally won't need a kitchen is Las Vegas! An upgrade (besides a larger room) would be a room facing the Bellagio to see the famous fountains.
Bottom line: If you can get a good rate and are traveling with children or just want a quiet oasis to get back to at night-this is your place (and Mandarin Oriental as well). If you love having the casino action and general Vegas craziness IN your hotel-stay at any of the other 4/5 star hotels on the strip.