All the RAID discussion on the list was about the Linux MD/DM software RAID. It isn't as reliable as other options.
From what I gather, MD does not use write-intent logging by default, and when it is enabled it is very inefficient. Probably because it doesn't spread the write intent logs around the disks. Also, MD does not detect a unclean shutdown, so it does not start a RAID scrub and go into read+verify mode. And all that is a problem even when the array isn't degraded.
And of course it doesn't have a battery backup. :)
All that said, Linux MD hasn't given me any problems, and I prefer it over most cheap hardware RAID.