I have "-f 60" in my flags and I notice no degrade in performance. I can even play games with a decent framerate while mining (>90fps on Counter-strike Source), of course my hashrate drops during gameplay though.
Pretty much this. I have a HD5770 and am still able to play Left 4 Dead 2 at max settings, 1920x1080 at least 60fps. Not sure what my hash rates are, but it doesn't stop me from playing.
Also means I don't have to remember to start/stop the miner when I want to game.
GPU mining while browsing internet or something is barely noticeable. Suggest that you do turn off hardware acclereation for Flash/videos as that will decrease the hash rate. And any recent CPU should be able to play flash fine without hardware accleration anyways.
I already gathered from the BC Wiki that it's not possible to share the GPU between a game and a miner at the same time.
What do you mean by this? The performance will be lowered, and but it is possible to game/mine at the same time.