Currently I only own the Nikkor 18-135mm, so I guess you could say it's my walk around lens
I love it, and basically shoot throughout the range in a typical photography trip
It's reasonably slow throughout the range (3.5-5.6), but since most of my shooting is done in bright Western Australian sunshine I've never found it particularly limiting.
I've thought about getting something like the 17-55mm Nikkor, but I firmly suspect that it would have a negligable impact on my ability to take great photos at this stage. If I can't produce amazing stuff with my current lens, I can't see how having a faster, sharper, and less barrel-distorted lens will magically help with my shot composition and framing skills and understanding of how to work with light...
When I feel that I've got a firm grip on the skills that underpin taking excellent photos, and that I'm being held back by my current walkaround, then I'll make the move
I'm a gadget lover too, and I'm not for a moment suggesting that better lenses don't open up new opportunities, allow you to extend your skills, and make taking great photos easier, but the cynic in me somethimes thinks that some people on here care more about their equipment and its specifications than learning to take and taking great photos
Not entirely sure how I ended up there, but anywho.
I'd suggest to the OP that he needs more wideangle cowbell in a walk around lens