We use dlt and sdlt drives. The sdlt we use are 160/320. Seem fairly reliable , but are pretty pricey. I think a bare SDLT drive is about 3000 US $ . Sdlt tapes are around 40-60 bucks per, so depeding on they cycle you want it can get pricey. If you need a new scsi card thats a good 360 US $ also.

The firewire external drive scenario looks like it may be a good option, just be careful with magnetic fields and such. External drives would also be much cheaper.

Ive used backup exec and its okay. Not too many complaints, but it is the only thing ive used.

DDS4 sucks too. DDS5 probably sucks too.