I have the Tamron 17-50 f2.8, and I think that it is much better than the 18-55 kit for general purposes because of the large aperture.
That said, the kit is a very nice landscape lens with tripod and wired remote (the remote makes it pretty easy to use CP even with the rotating front end of the kit). The kit lens is sharp at f8 in the middle part of its range (the kit is certainly acceptable but not great at 18-20 or above 50mm). Many will disagree, but I actually like the kit focal length better than the Tamron (for my uses, the 55 on the kit long end is a bit more useful than the 17 on the Tamron wide end).
The kit is great for hiking; it's light and small. Yeah, it doesn't seem to be durable, but it's expendable.
RP, 60D, RF 24-105mm f/4-7.1 IS, RF 35mm f/1.8 IS, RF 50mm f/1.8, EF-S 10-22mm f/3.5-4.5, EF-S 18-135mm 3.5-5.6 IS, EF-S 55-250mm f/4-5.6 IS, Tamron 17-50mm f/2.8, EF 28mm f/1.8, EF 50mm f/1.8, EF-S 60mm f/2.8 macro, EF 85mm f/1.8, El-100, 430ex, 220ex, Alien Bee B400 (2), Alien Bee B800 (2)