After upgrading to Mavericks your Drobo might not show up in Finder (here it did just fine, using a Drobo FS800 (aka 2nd gen Drobo) connected over Firewire). If that happens, do either one of these to get your Drobo visible in Finder again:
Unmount the Drobo from Disk Utility (where it by magic will appear!?) and mount it again by reconnecting it to your Mac.
Unplug and put back the power to your Drobo, after which it will restart.
One of those should do the trick in case your Drobo might be missing.
This post is outdated. Not everything is accurate anymore. More than three years later I still have my Drobo running and have performed disk swaps without any problems. Drobo has grown up by now. One remaining issue though is the speed (although that should be better with the newer models): it’s not optimal.
A few months ago I bought a Drobo. Ever since I’ve been getting questions of future Drobo owners if the device is any good, what I use it for and if they should buy it too. I must say that I find it tough to answer them, as I have mixed feelings about this product.