I'm going to look at buying a 20D that comes with a Canon 28-135. Focal lengths aside, is there any reason why I wouldn't be happy with this as a walk-about lens? I'm an intern at a studio, so any serious shooting I do will be with those lenses and cameras at the studio, but I still wanted a Canon myself (I switched to Nikon for a bit...).
Anyway, if I like the lens, I'll use it, but is there anything to look out for specifically with this lens or any reason why it wouldn't be the best choice? I figure if it has decent build, USM, full-time manual, and IS, those factors would outweigh the disadvantage of the variable aperture. I've had bad luck with non-Canon lenses, so I definitely feel more comfortable with this than something like a Sigma 24-70 or Tamron 28-75.
Does anyone have any experience using this lens as a walk-about lens, and what are your thoughts? Thanks!