I've owned the 100 L and the 90 tammy, i have kept the tamron, and i have had nikon canon and sony versions of the tamron. All have been superb optics and for the the money they are awesome, Really loud Af though - but i don't shoot enough macro so the canon L was a waste for me, but its also a fantastic lens (real world photos you can't tell the difference between it and the tammy)

Ah okay thats good to know. I'll be stacking the extension tubes on the lens as well for the most part so I'll be focusing manually 95% of the time.

they are quality lenses as is, you would loose too much on the sale of them and purchace of the newer versions, rather spend that money on another lens or other gear

good advice in here i will be taking on board too =)