I've had the 15-85 for a few weeks and it has graced the front of my camera more than any other, but before that it was the 24-105. Soon, I am going to switch back and then decide which one I truly like the most for general use.
The wide angle is great, but I find myself switching to the 50mm prime more often now since I have an f/5 rather than f/4 at this focal length. On the long end, I am switching a bit more often to telephoto, but there isn't a big difference between 85 and 105 in reality.
For travel, or just going to outdoor locations with no particular shoot in mind, the Tamron 18-270 is the lens I take. It will probably remain in this role and be in at least second place after I decide whether to leave the 15-85 or 24-105 in place most of the time.
This is a great thread -- The one real surprise is how many folks answered with fairly long lenses, and only one with a wide-angle.