
I got the WD Velociraptor some time ago.
Was oscillating between it and some random SSD.
I'm glad I chose it (SSDs had too many unknowns, uncertainties and sometimes strange performing reports).
A 5min Windows boot time turned to tens of seconds (with all little & unneeded programs loaded [and i got plenty]).
The very first time I boot from it (btw, it has a very nice program on their site which basically clones the primary partition so you can boot right away from the new disk) when I logged in EVERYTHING loaded and after it did, only AFTER, did the Windows Start-up sound play. Needless to say it impressed me. Of course performance degraded over time but it's insignificant (e.g. the start-up sound plays later now

).
Gaming-wise I don't feel any improvment really. TF2 loading times are the same I think, but they never were long to begin with. Haven't played anything else much so it's not a verdict, however I am suspecting a bottleneck in another PC component.
But yeah, SSDs are the future.
Regarding defragmenting them: it's counter-productive. As previously stated it's intended only for hard DISKS. Defragmenting a SSD shortens it's life span because you're just wearing the device off without any purpose. They still support bad sectors though

.