Using ESXi 4.1 on Dell servers we have installed a 6Gb SAS-HBA card into the server and used Hardware Pass Through. The Tape Library is Dell TD-2000 and has LTO5 drive in it, so this is a library not a standalone drive, but the same circumstances would be the case for standalone drive as drive is connected to the SAS-HBA.
This system has been in place, without issues for >12 months. Performance hass been very good with transfer rates >2.5Gb/min. The throughput hass been limited due to our backup SAN only having 2 * 1Gb NICs.
Last month wee changed the SAS-HBA for a SAS-iSCSI bridge. This has also worked without incident but the throughput has dropped significantly because of the 2 * 1Gb NICs in the bridge rather than the 6Gb SAS interface in the SAS-HBA card. I would recommend that 10Gb NICs are the minimum requirement for SAS-iSCSI tape integration.