I'm all for the 100L, but can I ask why you haven't bought any fast primes up until this point? (28 1.8, sigma 30 1.4, 50 1.4/1.8, 85 1.8). L Disease? Only shooting outdoor in good light? All have very nice apertures and are at least as sharp as your current glass stopped down a bit. You've spent so much on some amazing zoom lenses (all of which I have and love) but didn't even get a nifty fifty along the way.


Instead of the 100L, you could consider the ef-s 60 macro. I really liked that lens and only upgraded to the 100 non-L when I went FF recently. It's a lot cheaper and also about half the size or smaller than the 100 options. IS is great but I've never thought it was would be that huge of an advantage for macro. At macro magnification even the slightest breeze shows up as pretty significant subject motion on flowers for example. It also won't make focusing that much easier since I find handheld macro focusing has a lot to do with your forward/backward motion which the 100L's IS doesn't account for. I'm sure it's good for completely stationary objects since macro requires so much light, but that still doesn't seem worth it to me. Maybe I'm missing something that makes it worth the added costs. To me it seems like you have a big whole in your kit (fast primes) that I'd rather see you spend that extra money on, but that depends largely on your photography needs. 60 macro + 50 1.4 or 85 1.8 would be money and camera bag space better spent in my mind.


I stress the size of the 60 because I personally rarely go out intending to shoot macro. It happens, but a lot of macro stuff also comes from having my macro lens in my kit when I went out on a nice day. This is easier done with the 60, but then again if you're lugging the 100-400L around then size and weight probably aren't much of a concern :P


-Yoni