Does anyone have the sales numbers handy for USA in '08 and '09? I'd be surprised if M3 sales in '09 didn't drop by at least half of the '08 numbers.
In other words, you'll have to pay a premium for the 09's, just because there are fewer (yet they're in demand due to warranty & people not wanting to buy the 1st year of a model).
I was on the fence about 08's, but I eventually decided that even if there are a few problems yet to surface with the 08's, the price difference was enough to cover the cost of a few major repairs. And when you finally do sell it, the going rate for both will be about the same.