I have had many BMWs, and I think I like the sport seats on our X3 the least. Seat comfort is so subjective and varies greatly by individual...my fiance loves them, and it's her DD, so I can't complain. For me, I just can't seem to get in a comfortable position or modify the bolsters enough to feel natural...they feel almost too narrow and firm. Per your question, at 15k miles, I can't say I've felt much break-in. On the plus side, maybe that means they will preserve their aesthetics well over time.
Amen to the multicounter seat...loved them in my '05 X5 4.8is.