I would sell the Tamron and buy the Canon 17-55 f/2.8 IS. I've used this lens quite a bit for wedding photography, and it focuses very quickly. I can't compare it directly to the Tamron, but I certainly didn't think the focus was holding anything up. The real factor here is Image Stabilization. This lens is hand-holdable to 1/8 second or less depending on how steady you are. That is just something you can't get anywhere else, even in the 24-70 f/2.8 L. I can attest the Image Stabilization of the Canon lens is phenomenal. Also, the lens is much sharper than I would have ever expected, even wide open.


For your second dilemma, I would hang onto your canon 200 f/2.8 until you've saved up enough for the 70-200. It's up to you whether you get the f/2.8 or the f/4, but again, i wouldn't even consider a non-IS lens. I know the f/2.8 lens is very expensive, I just bought it about a month ago. So if you want to save some money, you could probably get away with the f/4 lens. The IS will make up for the lack of lens speed in most situations. And I've read that the f/4 is sharper than the f/2.8, although that would be a tall order, it's the sharpest lens I've ever shot.


Good luck. Just want to make sure you don't end up repeating my mistake of buying inferior lenses just to have the focal length covered, and then going back and selling them to get cash for the lenses I really wanted in the first place.