I was going to buy one of these six months ago. I needed it to replace a 1Tb My Book. The price at the time was $780 from a local reseller. Two weeks ago I looked at it again. It was going to cost just over $1000. Shocking, but I thought I could stretch it. I then optioned it using the Drobo site's
Drobolator and was shocked to realise that I would have to buy at least one 1Tb drive to combine with my current crop of drives just to get it up to 1Tb usable space, which would give me no advantage whatsoever. I would have to buy at least 2 1Tb drives to get any extra space, and that priced it beyond any feasibility at this time ($1400). Instead, I bought a 2Tb My Book for $670. I use a combination of my original 1Tb My Book and a 500Gb USB drive to back up my stuff at the moment. I'm happy with the new My Book.
The Drobo costs more than your ordinary case but I think it's well worth the money. The only knock against it is our shit exchange rate, not Drobo's fault. I think if you're visiting the US and can buy one there, it would be viable. They only cost $500US. That's about $780AUS at the moment. Reseller markup of $220AUS kills the value.