Be sure the 08 wasn't a demo. Demo's get abused to no end. Doesn't sound like that great of a deal to me unless the M is optioned out a bit, but I'm not in tune with US prices. What are the options on the M3? Does it have the tech or premium package or DCT?
I saw a US spec AW 09 coupe with 1800 miles that was traded in going for 46K at the dealer. Only option was Ipod/USB adapter. Bone head traded it it for an optioned out 335.
IMO I don't think they should sell a 335 w/o the sport package. Seats alone are worth it.