Before upgrading I check here to see if there are reports of problems. There were some, but no reports of "no problems" that I could see. I hesitatated but, decided that most people with no problems wouldn't bother to post, and so I went ahead after making backups of both files and database.
Everything went fine.
I had only one small issue. When prompted for my API key for Akismet I inadvertently entered the wrong one, and was then unable to find it online--it is NOT in my wordpress.com profile as indicated. However, on rechecking what I entered I found the problem and was able to fix it.
So, everything's ok apart from not knowing where my API code is.