speedup with M2090 vs C2070?

What kind of speedups are you getting when switching from C2070 to M2090 cards?

Did you have to do some fine-tuning to increase the speedup, and how did you
go about that?

Is buying M2090 cards a good investment, given that the Kepler cards are coming
later this year or in Q1 of 2012?

What are the differences between the Nvidia, HP, and Supermicro versions of M2090?