Also think about speed. A hardware RAID controller will be hella faster. It'll have onboard cache and such.

Whilst I don't dispute that, I don't think that it's that relevant. RAID5 takes a huge hit during the write - every drive must be read in order to calculate parity. Read performance is much better. For a web server or media vault, RAID5 is ideal, for a syslog server, not so. That being said, a hardware RAID5 implementation should be significantly better than a software implementation.

This is a MICROSOFT implementation

That would be my concern.