Hi, I've just looked at v3.9, so this might be already fixed for v4.0 final, but:

The find algorithm seems to have problems with wraparound lines: if the display position for the found string is set to top or middle, the line I'm looking for is 'displayed' off screen somewhere... This happens only with 'big' documents, the ones with lots of wraparound lines.

Other than that, excellent stuff. Don Ho, you're an inspiration to us all! :)