I had an environment with 12 ProtecTIER systems at my last job. Dedup rates that I saw were in the 4:1 to 6:1 for TSM backups. My biggest complaint was the single stream performance. While in aggregate the system could achieve the documented 400MB/s speeds, a single session could only achieve up to 20MB/s. Had to get at least 16 concurrent streams going to get the performance where it needed to be.
As I recall ProtecTIER was going to be offering nfs and cifs connectivity next year, but they told me that several years in a row, so I don't know where that is at.
I have been testing Data Domain with TSM but as nfs storage, not a VTL. This works quite well, after a couple months I see my TSM 5.5 backups achieving 9:1 dedup. This is all file system backups, no databases. So far my experience with DD has been positive.
-Al