GoFlex Desk is great so far. I have some high-track count/high-sampling rate sessions that choke every few seconds on Firewire. Thunderbolt GoFlex performs flawlessly in these sessions (40-80 tracks/surround/destructive punch across 8 record tracks).
OS X sees the disk as SATA, and the performance is on par with what you would get with the same physical disk inside a Mac Pro. My Thunderbolt chain is MacBook Pro>GoFlex>external monitor.
Weirdly, I hear the drive do an occasional access "click" when I'm
not in Pro Tools, and that will stop Soundminer playback. This has only happened a few times, and never
in Pro Tools, so I'm not at all bothered by it. I suspect it has to do with the drive mechanism itself and not the GoFlex/Thunderbolt architecture. I will likely turn this GoFlex into my mobile hard drive, and buy more in the future. Seagate's website could be much clearer when it comes to GoFlex accessories. There are eSATA and Firewire mounts for the modular GoFlex drive enclosures. Also, there is a separate line of GoFlex Portable that are all 2.5" disks. "Desk" is 3.5" disks.
Up until now, I was using exclusively
MacGurus Burly enclosures for eSATA. These are more cost-effective, and totally reliable.