Here at home on my iMac, I've been using OS X for about 4-5 months. Needless to say, once 10.1 came out and X finally felt like a "real", complete OS, it's all I run on both my home iMac and my G4 at work.
Of course, at work, using QuarkXPress, Photoshop, etc., I'm in Classic quite a bit, but everything else is in X (surfing, e-mail, iTunes, various utilities and apps).
Same for at home, although with Illustrator 10 now out, I hardly EVER launch Classic at home.
I am, however, waiting for a font management utility that's as transparent and easy to set up and use as ATM Deluxe. That's the only thing I'm missing right now.