The Sigma 18-50mm f2.8 is also worth considering, similar in price to the Tammy one too, also has IS
I have had both the Tammy 18-50mm non IS, and currently have the Sigma
In real world terms they are all pretty much the same, no noticeable difference, but having never owned either of them at the same time i have never compared like for like shooting the exact same subject with each lens, but i have never thought "damn i wish i still had the other one"
Only reason i changed is that i dabbled in FF for a while and sold my Tamron, then went back to crop and thought i'd give the Sigma a try, i have not been disappointed
I have also shot many gigs (local pubs/clubs) with both lenses and had some very good results, the last thing i'd want to be doing is changing lenses in some of the places i went to shoot bands