I've used a 4.5-5.6 APO DG for quite a few years. I like it, it was cheap and I've taken some great shots with it. It is however starting to feel it's age and, even on a tripod, the 300mm shots (birding) are quite soft and I'm reluctant to go past 200mm with it.
I just read a review of the Tamron AF 55-200 4.5-5.6 DI LD Macro, which came across as a low priced wonder. The short end coming down to 55mm would be a big bonus as I often find the the 70mm on the Sigma too long. It seems a good lens but then there is also the new Canon 55-250 STM which I gather is also very good for it's price point and has the big advantage of IS.
Any comments on these lenses much appreciated, my camera is a 450D and, although I've no immediate plans to upgrade, the chances are that in the next year or so the upgrade bug will bite and I'll take the plunge.
Light weight is a consideration as well since this will double as a holiday lens and needs to join the 450D/Tamron 28-75 and probably a 17-50 Tammy in the camera bag. Obviously, I want to keep the weight down and not feel as though I'm hauling a ton of gear (been there, done that before). If there are other contenders that is also fine, I'm not wedded to the idea of the other two.