Mike, I usually agree with everything you have to say, but I disagree (partially) with your USB 2.0 assessments. It's true that so many USB2 devices really suck, I'll agree that most of them do. But this is due to poor implementation and cheap/shoddy chipsets. It also didn't help that the G5 power Mac systems (pre-Quad) had crap USB2.0 chipsets themselves. I've got some USB2 drives that perform every bit as well as FW400 and on large sequential streams can even outdo it.
I've seen reports that drobo can easily sustain 35~50MB/s depending on which drives are used, so that looks promising. I'm not promoting it as a workhorse RAID, but a convenient desktop backup and data storage device with some fault-tolerance.
As for the Quantum 600A, I still have a hard time believing that Gigabit ethernet connectivity and the ability to handle MXF containers justifies a $5500 premium. Especially when it's not even compatible with all flavors of MXF, nor can the drive deal with clip data itself without using additional software, which really creates a problem for some installations. Or If I really think about it, I definitely do understand the price premium... It's like everything else that finds an industry niche. Premium prices for one or two features that are inconsequential to most users.