If you are OC simply for the "performance" 4ghz vs 4.3ghz is "only" 7.5% difference. That is the difference you really won't feel much. But if you look at it slightly different perspective, difference from stock, 3.4 vs 4 is 17.5% difference, and 3.4 vs 4.3 is 26.5% difference. If I were to choose 26.5% vs 17.5%, I would definitely choose 26.5%. I recommended to OC to 4.2 ~ 4.4ghz, because that is what majority of people, and most of my buddies, are setting to. I am not saying that is the "best" decision, but simply that would be "my" decision.
Overclocking at moderate~aggressive levels require lots of research, time and effort, so I think that is something everyone needs to understand before they try it.