Yes and No, dedup is analogous to compression, in fact is it a form a of compression in that in removes instances of identical data. But there are radical differences to the approach. Block compression works on very small data sets. A tape drive is compresses data in the order of 64k chunks. Whilst deduplication works over terabytes of data.
So I would expect to see some tangable benefit to CommVault's dedup with appropriate data. (lots of systems with similar types of data).
How CommVault backs up in the first place is another matter. CommVault's use of the NTFS change journal is poor. Ignoring any realtime requirenment you might have, changed journal is a batch process, the processing the change journal is an issue once there are lots of files. Also if you only want to process a subset of a volume, you have to process the change journal for the whole drive which means dinosaur backup products that do directory scans will often be faster. You may run into memory issues. You also need to make sure no other product is clearing the journals, etc, etc, etc.
Interesting reading the above comments on CommVault. Online, I dont see much in the way of other real user feedback, normally just hype from reps.
Other products that might be of interest are:
Acronis Backup 10. Had a play seems easy enough to use. Think its aimed at the home / small business but might be good enough for our needs. Has good reputation for Bare Metal Recovery.
Cofio AimStor. AIMstor is more appropriate to the multiserver backup market. Does realtime backup as well as traditional batch based backups of filesystems and applications. Also does Bare Metal Recovery similar to Acronis. Has a major funky interface, very polished, check the video. Worth checking if its your budget.
Lastly, Arkeia. Not tried this one yet but company been going a while.