I have a dual P4000 NDMP/SCSI hybrid with Legato Networker on a Solaris server.
The GigE NDMP drives appear as remote devices in Networker, I assume Netbackup has something similiar. In Networker, you just add a device as 'rd=drive-hostname:/dev/nst0'.
Jumbo frames are a must have. We've had our unit for about a year, but just upgraded the switch to one that supports jumbo frames. Backup speed went from 11MB/s without jumbo frames to 18MB/s with jumbo frames.
We've been generally happy with it. All enterprise backup sw/hw solutions suck, and this one doesn't suck to badly.
John