if you're overclocking with adaptive mode I would enable speedstep, if you're overclocking in manual mode I would disable it. The only real drawback with it disabled is your cpu won't downclock and it'll use more power and idle warmer.
I overclock in manual mode and have speedstep disabled.
Speedstep is a great feature and entirely compatible with OCing these days...
Just run adaptive voltage and speedstep on and you get all the benefits of OC performance and your CPU can downclock and downvolt when it needs to....win win
