Robster, if you get anything near 40 read and 29 write with real world bulk file ops, even very large files, with a V2 you should be quite happy. On Win XP and Win 7 USB I get 15MB/s real world and that’s on the better days. Win doesn’t deal well with FW, maybe somewhat similar to the way Macs don’t deal as well with USB from what I gather here and there.
A better upgrade for a V2 would be USB 3.0 because that is the only way Win users might reliably get the performance you are complaining about on FW800. We need it more than you do :-). Actually, FW800 is well beyond a V2’s capability although I’ve never understood why if that is so then why is USB 2.0 so poor, relative to what even USB 2.0 should be able to provide (more like mid 20’s at least, maybe 30 in ideal but likely not real world conditions).
Personally I would expect a Drobo S V3 with Thunderbolt since Apple has left Mac users mostly out in the cold with their lack of eSata support except when princely sums are extracted for the highest end Macs. A Drobo S would make sense.