I've been using CM7 ROM from the day I bought my Optimus M (About a month ago.) I had CM6 and then later CM7 on my Verizon Droid and became familiar with it. I left Verizon for MetroPCS when Android phones became available in my area (Flint, Michigan. We're !EONS! behind the rest of the world technology wise.), and seeing that I could use CM7 was awesome.
Anyway, I don't notice any abnormal battery usage on CM7. It might be a bit more than stock, and perhaps a bit more than even the Sense ROM, but at the end of the day after using it HEAVILY on both 1xRTT and WiFi, I still have around 45% battery life left. Then again, I'm also using the OC kernel and that might make a difference.
I've never used the Sense ROM, so I can't compare the two.
On a side note, I've never attempted emulators on my phone. I have a 1001 PSP thats modded to hades and back, and do all of my emulating on that. I've often wondered how certain emulators would work on a touch screen phone. (N64, PS1/2, even SNES!) Feedback would be awesome, because having Contra and TMNT Turtles in Time wherever I go would be superb!