I just (like, about the time you were writing your comment) replaced a pair of spinning disks with a pair of 120 GB SSDs in one of my machines here at home. It's not technically RAID but a ZFS mirror instead. The operating system and related files will live on it while my data still lives on some spinning disks (simply because of the amount of data).

I've got pretty much the same setup (albeit with several more spinning disks) in a bunch of servers and have yet to have any problems (* crosses fingers *).