Should I do it?
Can't afford both, but can sell my 135L for near full price (850), add $400, and get the 24-105L.
135L stellar but exotic for my uses. Use it about once every 2 weeks for a few shots then put it away but in a few months could get the 85 f1.8 or 50 f1.4 that would suit my (amature) portriat needs.
I thought the 135L would expand my creativity more, but mainly its shallow DOF (at f2.0) is hard to get used to and its not really long enough for a good tele. Is perfect for zoo or theater lense, but so would a 70-200 f2.8 that would also cover other needs.
I have a super sharp 28-75 f2.8 Tamron but would love to have IS, better & faster focusing, and a bit more of the wide and long without sacraficing anything in image quality.
2.8 is nice and I use it quite a bit, but I'm a beginner and it trips me up as often as it helps. Don't plan on selling the Tamron just because its such a good copy. If I don't find myself mounting the Tamron after 3 months, I may sell it.
My thinking; f4.0 will be equal on both lenses (Tamron vs Canon), and the Canon may even be better. Many more low light shots will come out due to IS. I'll get to explore 24mm more, and on the longer end, many shots that should be zoomed in a little more will be (with the 105 reach).
I'de truely feel emptier without the 135L, but I think the great walk-around IS L (24-105L) would put enough smiles on my face to compensate. And if it were spot welded to my 20D I probably wouldn't gripe too much.:p



The 28-135mm isn't even close. Not even remotely in the same league 
