Sheesh, while our talking about SSDs is kinda offtopic here, I'm just going to add one more penny to that.
Yesterday I've replaced a super old 40GB 3,5" platter drive in a CNC machine supervising computer for just your standard 120GB SSD. Cloned the partitions, and there we go - massive speed increase for about $30. Also need to consider reliability, too.
Now that I look at it, there isn't really any reason not to buy an SSD for any sort of new computer you're building, or switch to one on your current one. I've been looking at prices per GB of SSD storage steadily drop through the last couple years to as low as a third of what they were when I started observing them, this is just insane.
Or well, platter drives are still okay for bulk storage due to cost, but seriously, which typical user with steady Internet access does any large scale data collecting nowadays?