Jojo, that Sigma looks good. I plan on replacing my Tamron and kit lens with this lens. What do you think?
Hey Mike, the obvious strengths of the 1770 over the 2875 are the 17mm wide end, the close up ability, and IMO the slightly better build. Other than that, given a good copy of the Tamron, I don't think there is any area that the 1770 is optically better than the Di. AF speed and noise are almost identical, and the Tamron is FF compatible with f2.8 throughout.
For a lot of folks 28mm on a crop body is not ideal as a walkaround, but for others it's fine. I don't know what your preference is. I like having 17mm starting point myself, which is why I sold my (beloved) Sigma 24-70 f2.8. I may get one again though someday soon (just because).
The 1770DC is a good lens; actually as I've shot with it more, I think it is optically better than the 1785IS overall. But I doubt it's better than the Tamron 2875 (or the Sigma 1850EX or 2470EX). Every lens is a compromise. It all depends on what you want to do with it. I personally would think hard before letting a good copy of the Tamron go, at least for this DC lens. Hope this helps a little.
