I'll get some scores up later, but I thought I'd share results from a personally witnessed 'a why OC/what benefit' point of view.
I was using ARMA 2/Benchmark 1 to test. (Arma is far more CPU intensive than GPU.)
I had fraps going and it gives you the 'average' at the end.
On stock clocks, the average FPS was 42.
Turbo Enabled, 4 GHZ single core, 3.8GHZ all cores, average 43
At 4.7GHZ, average 52 FPS
While I watched these runs, the frames really chugged on stock and turbo. At 4.7ghz, the min frames were up to 15FPS higher on average.
(I also did a couple of OCed GPU card runs and the increase was about 3FPS.)
So yeah, an average 10+FPS jump on an OCed chip. In game, this results in a higher average/min frame rate with less slow down.
Not all games will show a distinct improvement with a CPU OC, but for those that do... worth it.