SSD's have a lot of merit where the operating system is concerned. The entire system just operates faster. But for music storage, the drive only needs to be fast enough to serve up the music. SATA is just fine for the music files themselves (unless, of course, you are going for a truly silent server of the fan-less variety).
Which brings up an interesting question:
The only issue is have with my Mac setup is iTunes loading time. It takes about 3 minutes for the spinning beach ball to sop so that I can listen to music. It worked perfectly until the library had 1100 or so CDs in it.
I realize that iTunes itself is just a database (the actual music files are stored on an external USB drive - with 2 additional back up drives as well that are not connected except to back up.) Given that, I can't see a reason why it is so darned slow.
Would switching to a SSD drive in my Mac Mini (2010 unibody 2.4 processor 8GB RAM) for the OS and applications improve this? I don't really care about boot time, as it is acceptable, and the Mini is only rebooted for software updates. It is on 24/7 for weeks at time.