I haven't done this under ML but back when Lion was new I tried installing on a software RAID. It worked, but there were some limitations:
Bootcamp doesn't work
Recovery partition isn't present
I ended up installing Lion and now ML on a single drive and using RAID in the other bays for data. I'd be interested to find out if things have changed with ML. Let me know if you get it working!
so far remember it being very very time consuming getting my software raid 0 to work with lion... haven't set aside the time yet to figure it out on my mac pro... anyone else upgraded from lion to mountain lion on a software raid 0 startup disk?
I did a clean install to SSD RAID0, no problems (other than no recovery partition and filevault won't work, which it mentions, and then goes ahead and installs). Followed by migration assistant to sync in all my stuff from a clone.
Zero issues so far and they fixed Disk Utility.app, it actually verifies and fixes software RAID0 again (it did not work for all of Lion).
And I did an upgrade install on my SSD raid 0 without problems. It gave me a little warning about the recovery partition feature, and then proceeded normally.