I would get black, but I looked at the tan one at Neiman's this past weekend and the leather is gorgeous. So soft and supple. I would still get the black one though. Check out the picture of Maggie Gyllenhal carrying it in the celebs thread. You can't go wrong with either, to be honest.
Tan pops more, but I personally would choose black -- I'm biased b/c I find this color easier to match. You can't go wrong with black or tan though, go with what your heart calls out for. Keep us updated on your decision.
Go for black if you wear a black coat, wear a lot of black, like to match. Go for the tan if you will commit to wearing it with everything (which you absolutely could). Having seen the tan again this weekend I might actually choose that. It all depends on whether you already have a great black bag. I didn't, which is why I got a black muse instead of another color. If you do already have a nice black bag, definitely get the tan. I hope this helps!