1) No regrets. My other color choice would have been Monte Carlo Blue, but they weren't taking individual paint orders for e90's when I ordered.
2) Bamboo beige (non-extended) with carbon leather.
3) I'm not obsessive about washing/swirls/etc. so I can't comment.
4) After a few simple mods (Edition grilles, IND painted side gills), I think the car looks great. The other day, a parking attendant just kept repeating, "Damn, look at that car!" over and over again. It was pretty funny.