I've got servers running software and hardware IDE RAID. I've not spent a lot of time spent a lot of time benchmarking them, but I've heard a number of reports suggesting that most hardware [IDE] RAID 0 or RAID 1 implementations are basically crap. To get a decent RAID 0 or RAID 1 card still cost a fair bit last time I looked, and doesn't neccesarily offer many benefits (specially if they have binary drivers, or only have drivers for some kernels, etc). On the other side of things, I also have a server with a 4 port 3Ware SATA RAID0/1/5 card in it, running a 360 GB RAID5 array. It was very painless to set up, and performance is good - as you'd expect. I've not tested software RAID 5 to compare however. If you can afford to drop a thousand dollars on a raid controller, then you get what you pay for :) 

  

 See also: [Software], [Hardware]