Got my MAME PC today and initial tests look good! Running Prehistoric Isle fullscreen at 1920x1080 32bit with HLSL on, I get ~850% with throttle off (F10). Vertical games I've tried run closer to 950%.
PC is a 4th gen i3-4130 @ 3.4Ghz, with 8GB RAM, BTW.
I'm well pleased with the rig so far, but I'll post any other significant findings I have, if need.