If you haven't already been there, I would strongly suggest checking out the lens sample threads at Photography-on-the.net:
http://photography-on-the.net/forum/...d.php?t=141406
FWIW, I use the 24-70 2.8L for my walkaround lens. It is big, but the quality is outstanding. I shoot with a 30D (Crop body) so the lens is equivalent to 38-112 on a full frame body. There are times when it would be nice to have something wider, but overall I am very happy with the lens.
This is a useful tool for comparing focal lengths:
http://www.tamroneurope.com/flc.htm
Good luck!