I used standard ol' Rust-oleum metallic paint from Ace Hardware, painted them a year ago and they still look perfect, no chips.
http://i374.photobucket.com/albums/o...psgcvqm7c7.jpg
Pulled off the calipers, scrubbed them with a steel brush to get all the rust and crap off, doused them with brake cleaner then hit em with a few coats of metallic. I realize the tape job is overkill, but whatev
http://i374.photobucket.com/albums/o...pse92pt4ip.jpg
I'm a big fan of the subtle, clean look. I want someone to look at my car and think "damn that looks really nice", but not really be able to point out why. I'm not a real flashy guy. Not that I don't also like the colored (red, yellow, blue) calipers look, but I'd want it on an M3 with a big brake kit, or at least a car slightly more exotic than my 330i :)