Overclocking really was worth it back in the day of single cores, a t-bird and cheap amd rig would still struggle doing things like encoding, could take hours and hours to dooo something fairly simple. These days though clock speeds aren't hugely improved a far more complex encode takes far less time, and whack 4 cores on it and it becomes silly.
Its kind of similar at the moment to how internet went, you'd download a film at 56k, and want to shoot yourself, 17 weeks later it was done and a upgrade to your net connection meant you got things faster. But there was a point past which it became not over the top, just fast enough. You can now download pretty much a 1080p encode of something faster than you can watch them. Ok maybe not a 30gb bluray size file, but a very high quality 8-12gb encode of a film many people can download faster than the time it takes to watch the film. More speed would simply mean more time spent with the connection idle, rather than you being able to watch more, you can only watch so much film/tv/play games/spank it a day.
We're kind of at that point with cpu's. It used to be I might run an encode of something overnight so it didn't lag my computer down all day long, now I can run it while playing a game without seeing anything more than the slightest of slowdown that I really don't notice. If I run my quad at stock, 3Ghz, or 4Ghz, the difference is how much time my quad spends Idle once its done, not what else is it waiting to do.
I used to see a big difference with overclocking a low end chip and getting top end performance. Now I can't tell the difference in anything but benchmarks between stock and a 33% overclock.
But this is largely because the move from dual to quad was very quick and with consoles coming in the middle with limited/set hardware few games have moved beyond them just yet. For most of us the hardest thing we run is gaming and realistically any old dual/quad will feel identical to an overclocked 7Ghz i7.
These days I just tend to overclock as far as stock voltage will take me for a minor power hit but being able to keep all powersaving functions enabled for lower idle power usage. GPU's on the otherhand for gaming are still worth overclocking as we still have the situation where a cheaper gpu and making do aswell as overclocking the bejesus out of it gets you more value. You could just buy a 5970 and max out every game at 1920x1200 without overclocking, buta 5850 and overclocking it is just so much cheaper that I'd prefer to do that.
I think this is the basic issue, a decent dual core and a cheap quad core aren't priced £200 apart unlike a 5850/5970. A decent dual core at £50-60, or a great quad core at £120. CPU prices are so competitive with so little difference between the low end quads and top end quads even a budget quad is hugely powerful.
