It seems that it runs a lot cooler on wifi than using 3G. I struggle to hit 100F over wifi after streaming iheartradio, browsing, using phonemypc, etc over an extended period. I didn't have wifi access today and had to use 3G and I shot up to 110F rather quickly.
mine is actually cooler on wifi but on par with other roms (bugless beast and CM) when connected to 3G. I'm using whatever kernel the original alpha rom came with.
Oh I'm using the lower voltage kernel I think may not be who knows but I've been trying out the different kernels to see what happens. Didn't try one due to not having the WiFi updated portion