I love the casino hotels like the next guy. Bellagio, Wynn, etc.
But the true nicest hotels IMHO are the Four Seasons and Mandarin Oriental - both without casinos. The FS is undergoing renovation and isn't really my style. The MO, however, is ultra modern refined luxury and fits me perfectly.
I just completed a stay there in a 1400 sq ft Apex Suite overlooking the strip. Floor to ceiling windows on three sides, it was almost half the floor it seemed. Kitchen, dining room, living room, bedroom at the apex of the building and a bathroom with the sinks overlooking the strip which was larger than my own bedroom at home.
Full jacuzzi and steam sauna shower, it was really stunning. MO service beats almost anything else in Vegas and Twist by Pierre Gagnaire rivaled my dinner at the true Robuchon down the street at MGM.
Highly recommended.