I know that Doom 3 is right around the corner, but in the meantime, use those spare CPU cycles, and join the Zone 365 Folding @ Home team. The small handful of us (read 4, as of right now) have over 1,000 points and are looking to put up our 20th Work Unit (WU). Check our stats here. For more info on our team, you can check out the Zone 365 Folding At Home forum. Sit around, do nothing, but help cure disease: it's a win-win situation.
hehe, also I'd say the Consol version of the client is the most simple to use, but if you want, a user friendly interface get the other one!