I’ve been using two WD Raptor 10k RPM HDDs in stripe for 3 years or so.
Recently, I finally ordered my first SSD (RealSSD C300 by Crucial). And I was really shocked by the overall performance gain it provided to the system. Not the advertized boot time, but rather typical developer daily workflows, like Visual Studio tasks, MS SQL backup/restore/select/update/etc. and so on. Technically, the most important thing about SSDs in comparison to HDDs is that their performance doesn’t degrade in about two orders when it comes to random reads. So running several hard IO consuming tasks at once isn’t a problem at all.

I’ve made some tests before and after the switch and one video comparing Visual Studio load time with pretty heavy solution in it + ReSharper enabled:

As you see, VS load gets about 300% improvement. This is nice.

The CrystalDiskMark tests (notice the tremendous random IO difference):

WD Raptor 74GB 10000 RPM HDD (single one):

Crucial RealSSD C300 128G (SATA 3Gb/s mode):

Numbers speak for themselves.