Coming straight to the point, I just can't seem to play an FPS on the PS3 as fluidly as I could on my PC. The controller is just way too jacked up for me. I fail to understand why developers can't integrate the keyboard mouse setup to the PS3. There are exceptions of course like UT can be played with a keyboard,mouse setup, but for the most part this rule does not apply.
There is a device available 'FragFX' which supposed to map the Keybd,mouse combo well but since the damage is a 100$ I haven't had that much inclination to go and get one especially since V.2 of it is supposed to be even better but hasn't arrived yet.
For now I guess like most gamers I will have to keep getting used to the controller for FPS.:(