I've got a USB hub plugged into my superslim PS3 so I can attach a headset, the webcam, a PSP charging cable, and a wireless keyboard dongle all at the same time, and haven't had any problems so far. >_>b

I've played DUST 514 using said wireless keyboard and a wired mouse and it seems to go okay?

Maybe there's a difference between PS3 systems, or maybe it partly depends on how much power your devices draw. My wireless keyboard has its own batteries, and I suspect a big gaming keyboard with glowy lights would probably pull lots more power.