I actually have my Drobo connected via USB2 at the moment as well. There were some odd occurrences when plugged into FW800 that didn't leave me feeling secure. I believe these problems are related mostly to Windows and my (possibly) crappy FW800 card.

As for the Windows issues, Microsoft really likes making life more difficult than it has to be. I didn't realize the Drobo was acting slowly at first, because its primary function is acting as data storage. Then, I tried running a VM located on the Drobo. HOLY F***, was it painfully slow! That's when I stumbled upon the 1394b slowdown issue post-XP SP2.

I applied the patch (which wasn't needed in SP3), and then adjusted the registry settings. That worked to give me FW400 speeds, but why do I want that when I have FW800 ports?

So, in search of a solution, I came across UniBrain. They publish a freely-downloadable 1394b driver for Windows XP. In fact, TI (who made the chipset on my cheap card) suggests using the UniBrain driver for their chips. Unfortunately, the UniBrain drivers and the Drobo don't seem to get along. XP would see the two Drobo drives, but report a corrupt filesystem. That didn't make me feel too secure, so I'm running on trusty USB2 at the moment.

Another issue with Windows and the Drobo shows up when you boot Windows with the Drobo turned on. In most cases, Windows will not recognize the Drobo's 2nd drive without disconnecting and reconnecting after boot is complete. This is really silly and apparently not uncommon with FW devices supporting multiple drives.

Another problem which I can probably blame my cheap FW card on is shutdown. When the Drobo is connected and you attempt to soft-power off the computer, it will reboot instead. Really annoying.

Everything is working as it should with USB2, so I'm inclined to just settle on that connection. I may try FW800 again, but I will probably get a better card first.