Let me know your thoughts on this lens deciding on wheather its worth keeping. I don't use macro often but it may come in handy for wedding work.
It's an absolute keeper for portraits, and as you already used it you seem to be ok with the slower focusing speed (even with the focus limiter on, a full round trip takes a lot of time though probably less on a 1dx).
I'm using it with a 5d3 and a 6d, I couldn't imagine not shooting full frame.
... though the 100L is one of the lenses that are also very good with crop, and even beneficial for macro because of the larger working distance (180L-IS anyone?).