Having transferred about 200 tapes in the last two months, I will offer this advice:
--Get the DAT Recorder Serviced. Clean heads, new belts, etc will go a long way to avoiding issues with DATs.
--Pay Attention to the Output on the DAT. Most are AES, so you will need a compatible input to a recorder with a DAT or a converter box to SPDIF
--Shit Happens. About one out of 10 tapes are boogers, and require multiple passes to eliminate distortion and drop outs. I have not experience Digi-Noise.
--Either Listen to the Tapes As They Are Being Transferred, or Do a Thorough Master. I listen to each tape. I would not feel comfortable relying on software. The human ear is better engineered.