"This is a question I am often asked, and to be honest I do not really have a quick one line answer that properly addresses it. Back in the days when overclocking first began to gain popularity, it was certainly worth the effort. I remember overclocking my Celeron 300A from 300MHz to 475MHz, and boy did that make a noticeable difference. This was almost a 60% jump in frequency and at the time this had a huge impact on performance, as my relatively inexpensive Celeron system could now compete with the much more expensive Pentium II systems."
Around the PCSTATS Labs, overclocking has become a commodity, and really doesn't have much pull anymore. There are certainly lots of parts built with OC'ing in mind that scale to some very high levels, the net effect on software and games often seems muted by substantially good stock results... particularly when it comes to the upper spectrum of PC hardware. What do you think?