almost finished RF: Armageddon, i totally recommend it, it's got a decent length SP mode, (im at about 13h with still over 10% lefts to complete) when i've finished i will go and do some co-op infestation mode, (which is worth doing after SP because SP upgrades transfer over to MP infestation)
this game is my second best game this year after portal 2, and it's a bit better than Guerilla, which did have a tendancy to drag on when trying to liberate sectors. and the graphics are so much better.