Pros: The unit works perfectly on linux. Used mdadm to configure a RAID-0 system with two 1TB caviar blacks (WD1001FALS). Gives about 120 MBytes/sec write speed and 118 MBytes/sec read speed with the 2 disks on RAID-0 (each disk gives about 82 MBytes/sec and 107 MBytes/sec resply) using 'bonnie++' on Ubuntu 8.04. Not bad.

Cons: As another reviewer pointed out, you need to keep the disks about quarter of an inch into the tray for the disk to fit in properly. Actually, screwing it based on the holes (rather, the first hole) on the side worked for me. The drive must go in fully (so that it connects to the SATA II interface at the back). The outer door is slightly flimsy and you cannot see the LEDs clearly once you close it (just nitpicking).

Overall Review: Just make sure you connect it through the PCIe port multiplier given and not directly to the eSATA interface (if you have one) on the computer. "Quick HOWTO : Ch26 : Linux Software RAID - Linux Home Networking" is useful if you want to set up software RAID on linux. As another reviewer pointed out, when you boot (after connecting through the PCIe card), the RAID configuration tool in BIOS will be able to see only one hard drive. Just skip that and go ahead. You will be able to see all the disks once it fully boots and loads the drivers (use 'sudo fdisk -l" to list the drives). BTW, I set TLER-ON (Time-limited error recovery for WD drives) on the hard drives before using them in RAID.