So this is for those of us who have "old" MacBook Pro's. Old meaning 2010 or older mind you... you know, the MBP's that can't run AirPlay mirroring. From experience, how smooth/fast does ML run on these older MBP's? I have a 2009 C2D MBP with 4GB RAM. Lion isn't as fast as SL was, but it's smooth right now without any hiccups. How will ML fare?