Encore! Check out my review with photos
http://hubpages.com/hub/Encore-Las-Vegas
Aria and Vdara
http://mgmmirage.com/ may also be good options since they're brand new luxury hotels in MGM Mirage's CityCenter... no gimmicks like pirates, mummies, clowns, etc.
I also agree with Chip O. that Mandalay Bay is the best value for the money. I stayed there December 2008
http://hubpages.com/hub/Mandalay-Bay-Las…
and when I checked their rates yesterday it was $180 for two nights in mid December (compared to $350 for Encore and $300 for Caesars Augustus Tower) but they're also giving $100 resort credit on certain dates. So you'd actually pay $40 per night for two nights which is incredible. Having stayed at both MB and Encore in the past year I can tell you they aren't that much different; the rooms are nearly identical.
Encore's rooms are slightly larger and have remote controls for the drapes, lights, and "Do not disturb" sign. The rooms at both hotels offer a giant flat panel TV mounted on the wall, floor to ceiling windows, fridge stocked with drinks, in room snacks, and dual sinks in the bathroom plus a 2nd TV built into the bathroom mirror.