Claude is helping me learn French right now. I am using it as a supplementary tutor for a class I am taking. I have caught it in a couple of mistakes, but generally it seems to be working pretty well.
When I was in grad school my faculty advisor joked to me that to accurately estimate any medium to large software project, take your best estimate and multiply it by 3. If hardware is involved, multiply by 8.
Yes, he was telling me this tongue in cheek, but in my actual experience this has been eerily accurate.