Good question... the plan was always to buy a new F80, but I just can't wait. It doesn't seem to make sense to buy a new M3 and then trade it in just two years later.
I tend to keep cars for a while, so I don't mind spending $65k or $70k on a car I will keep for 5+ years. It seems excessive to do that for a car that I will only keep for a few years.
Maybe I'm wrong... maybe the depreciation hit on a new vs used is pretty similar. I'll have to do some math and see how it works out.