If you can afford one, buy one. I would. You're unlikely to see a car like this in the US probably ever again. Also, I'd never buy an M3 in my 20s. The insurance is likely to be insane and at least worth checking into as it may contribute significantly to the overall ownership cost. I also think that M3's are a hey look at me car, but that's my hangup. The 335D is just about the ultimate sleeper car and I actually wish they'd tuned it for a bit less power.
I can't find it now. It was something I read via Flipboard months ago and was a head to head of the Sub and Scion. The author noted flaws (not major) with both incarnations. IIRC something about a transmission in one and buzziness in both and something else. It could have just been a pissy journalist.