I recently installed a Drobo pro to a customer's site. The install was so simple and I was able to click "quick connect" within Microsoft ISCSI initiator.
I think the DROBO pro or elite are excellent pieces of hardware. They are not practical for file servers but perfect for non critical data or even DPM backups.
One of the most common problems I face , Is DPM Servers running out of space. And each HP 1TB Sata Server disk is very expensive. So rather than spend big on a server spend it on a drobo , We could virtualise DPM and via ISCSI present a Drobo volume to DPM which can then be used for Dpm Backups.
When Drobo support SATA III , The gap will begin to close between SATA and SAS which could make it a very interesting product.
You can buy a Drobo pro with 16TB of storage for approx €2k!!!