Mike,
I have stopped using NDMP totally. I was hoping it was like a "iscsi for tape" solution.
We used iscsi luns and if I created a 100GB lun it would be backup up as a 100GB lun in Arcserve even if I am using 10GB.
Arcserve's implmentation was pretty weak in my opinion and the support staff were not knowledgeable enough to help me in my case at least.
For me I am hoping for iscsi tape drives to become more prevelant and also working towards disk based backups.
I am in the SMB arena using ESX3.x and I would not really want to connect a tape drive directly to a ESX host, not sure if and how it would work.....
If you have more questions please let me kno