I just inquired about software RAID over at rackspace, with whom we host our server, and they said that they don't offer it:
"Currently we do not configure software raids. [...] we honestly do not recommend software raid as it is routinely unstable and doesnt provide the same redundancy as hardware raid."
"I would like to reiterate the point that the reason we do not offer software RAID solutions is because they are unstable and not as effective as hardware RAID."
Are they just plain wrong about this?