Really should think about RAID with today's multi-terabyte drives. We're getting to the point where the "Unrecoverable Bit Error" (UBE) of drives is near the size of drives.
So re-silvering (rebuilding) a RAID group after a drive failure requires nearly the number read/writes as the drives are spec'ed for. If a UBE occurs or two or more drives fail, you've effectively lost your data.
Personally, I'd go either go RAID1 or forget RAID. In all cases, back up your data. Tape drives cost a bit, but you can store multiple copies off-site and recover data much faster than over Internet. Pipe data through compression, then encryption before writing to tape and it's secure.
As far as hardware RAID controllers, the main downside is if anything proprietary is written by the controller and either that version becomes unavailable or the company goes out of business, you'll have trouble if the controller fails.
People who've had to deal with their karma are more interesting to talk to.