Obviously nobody cares what I think, so perhaps you would prefer the words of Armin Ronacher, the creator of Flask.
I've migrated literally, 10s of thousands, of files from py2 to 3. I've yet to encounter an issue with surrogateescapes or sys.stdin. Unicode issues yes, but mostly because we were previously being fast-and-loose with unicode vs. bytes, and mishandling, for example, emojis.