In the DC/Balto area I am in I don't come across that many e9x m3s unless at an event. I think over one and a half years of ownership I've seen (maybe I should say noticed) maybe 6 m3s on the road, and when they have noticed me I've gotten the thumbs up (about half the time I think). Also got a thumbs up from an e39 m5 and most humorously from a Prius driver at a stoplight in downtown Baltimore. I am always happy to return the gesture. Twice I have had guys come up to me complimenting me on the car at gas stations.
Have never gotten hate, a modded e46 I think 330 tried to race me the other day and I had a Mercedes SL 65 AMG throw down the gauntlet once. I have spent enough time in traffic court to just pull into the slow lane and drive the speed limit in response to that craziness. Especially when it is an SL 65 AMG, no point in embarrassing myself.
I would guess it is regional...
"This is like having a house-cat thatís a bengal tiger." - Todd Deeken, everydaydriver.com, on owning an e90 m3.