I went with the 24-105mm f/4L, for the extra reach, and I regret it. It's as people say, the 24mm isn't wide enough for indoor use. f/4 isn't fast enough for indoor use (and anything over f/2.8 lowers autofocus precision).

If you're considering the Canon 17-55mm f/2.8 IS, but are on a tight budget, then also consider the Tamron's 17-50mm f/2.8 (non VC version). It gets plenty rave reviews too. Not quite as good as the Canon 17-55mm f/2.8 IS, but it's half the price. In fact, with the savings, you can easily get a nice fast prime like the 85mm f/1.8 to help cover the lost focal length, or a flash to help with indoors.

If you do find yourself bumping up against the 55mm boundary all the time with your kit lens, then the 15-85mm may be the better option for you. If you go this route, and you don't know why people suggest fast primes, then add a 50mm f/1.8 onto your order. It's like $100, and it will open up new areas in low-light and thin depth of field photography for you. If you don't need convincing about that a fast prime is a good investment, or you're willing to believe strangers on the internet, then you might want to skip that lens, and invest in a higher quality prime, like the 50mm f/1.4 or the 85mm f/1.8 at some point. The 50mm 1/f.8 is a nice lens, and we still use ours, but it's build quality isn't the best.