amo, it is a good idea to do regular maintainence work using osx. there are still some problems youjust won't cure with fsck -y or disk utility. How often depends on ho you use your mac and how often. certain activities are going to leave temps scattered around your hd more than others.
here is a repost of my previous report of defraggers
below is my run down on the three i have used. i prefer and recomend the plus optimizer/diskwarrior combo but i would add that both are very simple interfaces. techtool pro is by far the most imformative and comprehensive tool, but i had at least one instance lately where only diskwarrior saved my disk.
1. techtool pro - also a good diagnostic and repair tool, includes a virus checker. is perhaps the best value of all. defrag is done seperately from optimization and will at times only defrag if certain conditions are not met. claims to be completely safe in preventing loss of data in case of interruption. drawback - slowest of the three.
2. optimizer plus - can be bought alone or with diskwarrior - i recommend getting the combo. diskwarrior saved my drive when all others failed recently. op is also interuption safe and does partials in case of obstacles. it is slightly faster than TTP. there is an osx version in the works but not out yet. it will be a paid upgrade as far as i know.
3. speed disk - part of Norton utilities which also diagnoses and repairs. fastest of them all. can lose all your data if interrupted. defrags and optimizes in one sweep but will not circumvent obstacles. least recommended but the one most people have because they advertise and promote the most .
the latest version of all these work with osx but must be run from another disk using 9.
i also have drive 10 and it does a good job of repair. At present drive10 does not have defragmentation but it should be in the next release. really all have something to offer, but some are more essential than others.
i would be glad to answer any more specific questions as well.
oh and going to
www.versiontracker.com and getting program called Xoptimize is good too. it will prebind your apps for faster launching.