Re: To Defrag or To Not Defrag...
I think it depends on what you're doing. In the modern day, drives seldom get full enough to fragment that much but if there's a lot of random file access such as in a database server then it's worth doing for performance. For most home uses, you're unlikely to notice a huge amount of difference.
Like Azrael said, if it's an SSD then all bets are off.