We currently use a Data Domain DD2500 as our main backup appliance and while the inline dedupe, compression and amount of data you can throw at it is great restores are still an issue for me on length of time to rehydrate the backups. Also lately I have been seeing some corruption of files as well.
From what I hear about Exagrid the Data Mover is built in to the appliance and there is the Hot landing zone which would make restoring way faster. I have never used one but hear great things and may look that direction at our next refresh possibly.
Chris Childerhose, VCAP-DCA, VMCE9, VCP, MCITP