Pros: Fast, quiet. I use Seagate 1.5TB (ST3150054AS) drives at 5900rpm and get very good (50+ MB/sec or so) transfers when directly connected (via 1Gb ethernet) to my ESX box (using a vmdk on an iSCSI share - many layers involved there).

Cons: The drive trays do feel a little flimsy - time will tell.

Overall Review: I've not tried many of the features - I am using it for Time Machine backups via AFP and to host a few iSCSI targets. I did upgrade the RAM, just because I had a space DDR2 SODIMM, the machine didn't seem too stressed otherwise.