Thank you both for taking the time to respond.  I know I could go with Sigma, Olivier, but I'd like to go with a Canon lens if I can.  The 17-40 seems to be quite a nice lens, though I've not spoken to anyone who has used it before.  I'm not quite sure what you mean, Danny, when you say "a bit less than the 24-70mm"... are you referring to less in price or less in all-around quality?  "IS"  is always a plus for me, because I generally surprise myself when I "thought" I had a good shot, only to see later a blurred shot because I moved or jerked the camera. :)  It sounds like you highly recommend the 24-70, except for the widest angle, which I would like to have for panoramic and general landscape shots.  Each of the lenses reviewed at: http://www.the-digital-picture.com/Reviews/Canon-Zoom-Lens-Reviews.aspx describe good and bad points, but all three sound so good, that I just can't decide.