look at it this way .. me for instance i dont like to wait very much loading times and speed issues are always on my mind .. when i boot up a computer that i took the time to build and use as a personal set up i want to feel like its one of the best systems out there .. just because its a hobby... its like asking why buy a ford focus when you can have the speed of a lotus... your computer is only as fast as its slowest componet .. so ssd drives are not for every one but some one like me i have a patriot wildfire drive 120 GB and a revo drive 3 240 Gb in my system its more about speed .. like i can load battle field 3 before any one else.. for instance.. if you do a lot of file conversion it helps because your processor can access the files faster
theres a lot of benefits but unless you buy one to try for your self .. you wont know .. for instance im thinking you would need at least 10 drives in raid 0 just to match one revo drive.. sure you will have a lot more storage space but your going to draw a lot more power too.. typical ssd drives also require less power.
I know I'm going to sound like a contrarian, but I'm considering purchasing an SSD or two for backing up my DVD and photo collection. I'll stick the SSD in an external enclosure and minimise the number of times I write to it, ie it will essentially be readonly. I'll add some voltage protection devices inside the case, if it doesn't already have any.
Obviously this doesn't make sense from a cost standpoint, but I'm more concerned with reliability than cost per GB. External rotating storage devices are very prone to mechanical shocks and high case temperatures.
As for speed, imagine how long it would take for a full format, or a complete virus scan, or a total backup, or a defrag, at 60 MB/s as opposed to 200 MB/s.
The difference is actually about 4 hours versus 14 hours.
Still another consideration is booting from a hibernated state. This requires that system RAM be restored from an image file on the HDD. A 4GB RAM image would require about 20 seconds at 200 MB/s, or 67 secs at 60 MB/s. (These times would be halved if the image were compressed.)