No it's legit and I have the expansion also which I thought updated it to V.1.3.
My video card is overclocked with the Catalyst ati-tool, but the temperature has never risen about 65-70 degrees celsius. Maybe I'll try putting it back to it's original settings. I know that I meet the minimum and maximum requirements to run doom at high, minus the 512mb of video ram it asked for to run Ultra. Heres my rig:
A8N32-SLI
AMD 3500+ 2.2gb
ATI X1800GTO 256mg
WD 250gb HDD
2gb Adata Vitesta ram
Artic cooler 64 CPU fan
BenQ DVD combo drive
I had this up and running on my crappy old emachine, which barely met the specs. I was running an aabit x600 video card, 512mb ram and a AMD3200+ S754 processor.