A lot of that depends on how you see the world. I'm a bit of a long-lens kind of guy -- in the film days, my walking-around lens was a 90mm/2.8 macro, and I don't think I shot more than a couple of hundred pictures wider than 50mm out of several tens of thousands.

The 24-105 is a great lens, but probably not the one you want if landscapes and travel photography are going to be a big part of your repertoire. The crop sensor means that the widest setting on the 24-105 is going to be the equivalent of just a hair under 40mm on full-frame 35mm. That really restricts the kinds of pictures you can take -- huge vistas and grand architecture (particularly in the sometimes narrow confines of European city streets) are going to be largely off the menu. On the other hand, if people and details are your main interests, you have most of the portrait and tight-crop range covered. Do note that the f/4 maximum aperture will somewhat restrict your ability to selectively focus -- you need to be pretty close in order to limit your depth of field to the subject at the wide-to-mid focal lengths. From all accounts, though, it's a superb studio lens.

The 17-55, on the other hand, gets you significantly wider at the wide end (equivalent to having a 28mm full-frame lens), but the 55mm end might be a little short for tight people shots (it's around the same as a 85-90mm lens on full-frame 35mm, which is okay until you go for tight head shots). The extra stop, though, means that it's easier to throw the background out of focus at the long end. Again, it depends on how you see the world -- 55mm is where my world starts, really, but I shoot people almost to the exclusion of everything else.

There may be a workable compromise in the offing, though, if you tend toward log-lens shooting. The "kit" 18-55mm lens is a perfectly adequate, if unspectacular, lens, and if you pick it up with the body, it should be dirt cheap. It may be something you don't use very often (and may not like using -- it doesn't feel nearly as good as either of the lenses you've mentioned) but it can be there in your bag (or jacket pocket -- it's pretty small) when you want to go a bit wider, and would make a reasonable companion to the 24-105 "everyday" lens.