So we've got two computers in the house using Intel Matrix raid.
First our server is using it for our Raid 1 boot drive, and my old desktop (just upgraded to an i7 iMac) was using it for its Raid 5 boot drive.
From what I've found, if WIndows crashes or isn't shutdown correctly the Raid will require rebuilding, both these systems do it. While it is rebuilding the performance is awful. It also takes up to 24hrs on our server to rebuild the array.
The other thing I have found is that the write performance on the Raid 5 drives is really really slow. My desktop was running it, bad idea I should have just stuck to a single drive, there was no real reason for using Raid.
Both systems aren't bad/slow (Q6600s with 8 and 4gb ram). We've also got a Raid 5 in the server running off a RaidCore PCI-X card and it is great. Never needs to rebuild and it is quick.
So yeah not surprising that the RaidCore actually works well but I didn't think Intel Matrix raid would be so bad...