Anyone used TESE?

So every time we get some good news, we also get bad. My husband had a 2nd SA and it came back nonexistent. His analysis a month prior was really bad (had a count of 1 million with 7% motility) but it would have been usable with ICSI. I can’t understand what would cause his analysis to be so much worse. We conceived our almost 2-year-old son on the first try.

Our RE wants us to do Testicular Sperm Extraction, but I dunno if I should expect much. The nurse who gave us the news is recommending having donor sperm on back up on the day of my retrieval. My husband and I are fine with donor sperm and even have vials on hold. My preference is still for a 100% biological child, though.

Has anyone had to use TESE and had any success?