Hi all, thanks for your replies. I upgraded rather than re-installed retrospect v10 software on both my retrospect backup server and network clients. I did raise a support ticket and the official response was:
"Looking at how much data you are backing up we would not expect much if at all of a performance increase for your environment. The speed and amount of time it is taking to do the snapshots looks good."
In my case I provided two data backup sets of 15.3 and 15.9 Gb. These were full backups, not incremental and the second one using a network based client. It's interesting that the analyst says they would not expect to see much of an improvement on such a low backup volume - even when the marking hype says their tests were on 24gb data sets! I also asked for the technical detail of the configuration used by retrospect to determine the 50% time improvement claimed in their literature, but they did not provide any answers in the support ticket.
Overall, I guess this improvement must be on incremental backups somehow, but who knows if Retrospect won't actually say how they calculated the 50% time savings in the first place.