I've had experience with both the VC and non-VC versions, as well as the Canon 17-55 2.8 IS:
Non-VC: I got it to upgrade the 18-55 kit lens. Its a nice upgrade coming from that. I think the build quality is better. The AF IS noisy, but you get used to it.
VC: I hated this thing. Perhaps my copy was defective, but the IS took about a half second to kick in after pressing the shutter button to focus. That means if it focused quickly, due to the distance of the previous shot being about the same, I'd have to wait a half second after that for the IS to kick in. Boo.
Overall, I'd recomend the non-VC because of its low(er) price, especially coming from a kit lens. The ability to have constant aperture is awesome, especially if you get into the whole strobist thing. On the other hand, the Canon does give better pictures in my opinion, and always having that in the back of your mind will bother you when using the Tamron. I eventually got the Canon and LOVE it compared to the Tamrons (it is a bit bigger/heavier though). The main complaint people have about it, that it gathers internal dust, is incredibly easy to fix yourself in under 5 minutes.
If you're patient, you can find your desired lens cheap enough used on eBay, that if you decide you don't like it, you can resell it and not lose any money. Its essentially a free, unliimited time, rental. I buy on eBay and resell on Amazon all the time to do this, and you can even MAKE a few bucks in the end if you get it cheap enough.http://thedigitalpicture.com/Reviews/Tamron-17-50mm-f-2.8-XR-Di-II-Lens-Review.aspxhttp://thedigitalpicture.com/Reviews/Tamron-17-50mm-f-2.8-XR-Di-II-VC-Lens-Review.aspxhttp://thedigitalpicture.com/Reviews/Canon-EF-S-17-55mm-f-2.8-IS-USM-Lens-Review.aspx