Actually I just did it a couple months ago. I had one of the first-gen'ish Micros with a failing headphone jack, got a full refund from best buy and rather than get another micro I opted for the sleek. It sounds similar, probably better (no a+b test possible here). I rotate KSC75s, SR125s and E3s with it (unamped).
Things it does better:
1) better grounding, I cant hear the microdrive in my E3s anymore
2) firware works better, no more random lockups (had newest firmware on the micro)
3) much better scroll pad
4) 20GB
5) full buttons that actually depress, no more paint flaking.
6) longer battery life. I get a full 18 hours out of it (E3s usually, no EQ).
Things it does worse:
1) Li-ion battery is not removable
have fun shopping.