they aren't really SATA-II, but they do have NCQ, which is nice. I got the new 300GB Diamondmax 10 from Maxtor, and it's really fast, mostly due to the 16MB buffer. Also, i believe that the SATA-II controller on the NF4 supports hot-swappable SATA drives (under the safely remove hardware thingy in windows, my HDD shows up, but i haven't tried it yet cause it isn't a spare. The seagate ones aren't that great cause they haven't released the 16MB versions yet, but they are on the way.
Oh, and by the way, NF4 rocks!!!!!!