We are users of Commvault and also DataDomain. Dedupe in CV (10x-12x) is not so good as on DD (14X-15X), but it's enough for us.
We've already decided to not use a dedupe appliance. Adquisition cost is very high and annual maintanance costs is also high.
We have a very limited budget (25-30K €/unit)
But as CV allow us to make some combinations with backup targets, we can buy more than a appliance to achieve our requeriments. We prefer a standalone system (less power, network ports, refrigeration, etc) but are not closed to other options