This post is outdated.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.