It's pretty highly regarded as an upgrade from the kit lens! Much more robust, and f/2.8 at the wide end.
If you don't use the 50-70mm range much, and can afford to spend a little extra, I'd strongly recommend the Tamron 17-50 f/2.8 (I've got one!) or the Sigma 18-50 f/2.8. Constant f/2.8 across the range is very nice, and not for too much extra cash. If you need a longer focal range though, I'm sure you won't be disappointed with the sigma 17-70!
Chris