Well... I get my miles "free" as I fly for work and get paid for it. So, I do already have lounge access (what I value most from having status) on *A and SkyTeam, which basically covers most of my flights. I always fly in Economy, but have been lucky enough to have been upgraded to Business twice, once for intra-Europe (only 2 hours!) and once for trans-Pacific.

Personally I guess I'd go for Economy, then get myself a bulkhead/exit row seat, and pray that I get an op-up to Business! :P I usually get a bulkhead/exit row seat on my flights anyway, or at least aisle, so I guess I'm quite lucky most of the time.