I used to have the 20-70 I until I sold it. Nice lens, heavy though and the new one is spendy. I now have the 24-105 that I got with my 5DMKII. I didn't think much of it (gah, must be mediocre since its a kit lens) until I realized that my best shots were coming with that lens. Now it's the one most often on my camera (next to the 16-35 II when I'm doing landscapes)
No interest in an updated 24-70, more expensive, heavier, limited focal range, no IS, but it's 2.8 (no biggie) ...