I debated renting it for awhile, and I still might. Considering the games are trickling in I thought i'd be fun to actually play the majority of games so far on the PS3 before it gets crazy like the PS2. I've never played any of the CoD games, so that's mainly why I thought I might try it. I just tire of the WW2 backdrop. I enkoyed that Resistance at least changed the history. I liked Medal of Honor 1 but playing 5 sequels of a FPS isn't really my thing when the controls weren't great to begin with being on a console and all (I prefer PC). I hope console FPSs add mouse/keyboard support more in the future.
Anyway, I suppose it would be more worth it for me since I haven't played any of them.