My first reaction to the question is to say "Yes". Keep it on the RAID.
However, while you are possibly stacking track upon track of your media files, and pulling bunches of data off of the RAID all at one time, the preview files are much easier to work with and a 7200rpm drive is just fine for such things.
Also, I suppose it depends on how much space you have on the SSD RAID. Since they are not going to slow down when they approach being full, it is probably fine to use them.
Personally, I keep all of my cache, preview files, temp files, and so on, on a separate RAID0 so that I can totally erase it now and then, defrag it, and know that I have the fastest and cleanest drive possible. But the guy I trust the most on this type of issue seems to think it is OK to keep the OS on one SSD and all of the other files on a big RAID.
In other words, do what feels right. You can justify it either way.
I have a solid state raid with 1 GB read/write and a 7200 rpm drive available.. where should I be storing the video preview files?
The raw files are on my raid and I figured since it's literally over 10 times faster than my mechanical it would better to just keep them on my raid as well?
I'd go the RAID option too. Give it a try - if it works it works. I don't think I've seperated project, audio, video and preview files since 2003 when I last used a Discreet Edit system..