I've been very happy with them so far. The only problems I have are with my Mac itself. I'm running an old Sawtooth, pretty much upgraded to the max. The old onboard FW bus gets funky every once in a while and burps on me causing the 2 RAID arrays to unmount themselves. When this happens I not only have to reboot the Mac, but the External drive too. It can get a bit tricky if I don't do it in just the right order. The other onboard FW has 3 CDRW/DVDRW drives daisy chained together. I have a USB2/FW card in a PCI slot that is driving 3 iPods (2 FW, 1 USB 2) and the fourth iPod is Daisy chained off the external drive bay.
All in all, this sometimes overwhelms my long in the tooth Mac and it starts dropping things off line, iPods, CDRW/DVDRW or RAID arrays. Ya never know how it's going to get weirded out next. Only upside it it doesn't happen often, once every couple of months. I chalk all this up to the fact that at one point I had 6 drives inside the silly thing and the temperature often reached, or exceeded, 140 degrees inside the case. That couldn't have been good for the board.
The 8 bay drive will come after I get a new Mac. Planning on picking up a Quad core G5 before the PowerMacs go Intel and get a lame name change. That could be as soon as 2 months or as much as 6 depending on finances.