Hi orangedial, the Tamron 17-50mm 2.8 is a very good choice indeed. Been looking at the reviews etc and studying the various feedback in CS threads...all very positive for this lens. In fact am considering buying it myself too so that I can upgrade from the D80 kit lens (18-135mm which is also actually quite a fantastic lens to start off with)
My only concern for your scenario (and mine too if i give up my 18-135mm) is that we will most certainly miss the added reach. In fact since you currently use the 18-55, my question to you is what do you do about shots in the 55-150-200mm range? Surely there must be times you need that extra reach beyond 55mm...i know that i do when I travel or zoo or taking longer range street/candids etc...
Well, the solution could be to fix that by combining it with a 55-200mm VR or a 70-300mm(Sigma etc)...but then that would involve changing lenses now & then and also the need to carry two lenses everywhere...quite troublesome (for me at least as usually have other paraphernelia like baby bags, pram etc etc in tow always....also when i travel). Alternately go for the best all in one solution currently in the market - the 18-200mm VR. However although the 18-200mm VR is a fantastic lens, the Tamron 17-50mm 2.8 will give much better results in the overlapping focal range...
This is becoming quite a difficult choice for me really...two very good lenses(17-50/2.8+70-300) or one good generalist(18-200 VR)...!? Hmmm...would love to hear your thoughts and also from other more experience fellow CS'ers....
(had a PM chat with your18 on this - he recommends the 18-200VR in the above choice...and he has actually used the Tamron 17-50 too...so a very good viewpoint there from him on these)
Cheers...happy weekend everyone!!