Have you looked @ the EX 24-135 f/2.8-4.5 it's just released... It's more compact and lighter than the EX 28-70 f/2.8 since neither is ultrasonic!
The EX 15-35 f/2.8-4 is... I think you'll need the wide angle too, 28mm is too tight on the 10D. Otherwise I think the EX 24-135 f/2.8-4.5 will give the EF28-135 f/3.5-5.6 IS USM (which I have) a lot of competition!