Well so far, he seems positively ecstatic about his flight this morning!

I'd say he has zero regrets, and good for him for going on this adventure. (I wish it was on a "real" Starship Enterprise, but I guess that will be a stretch before it becomes a reality.)
He may or may not have mentioned his own age, but what I noticed more in the interviews, (pre- and post-flight) this morning, was that it was the news reporters who kept pointing that out, not him.
If anything, I give him credit for showing the world that some older citizens are also capable of reaching for the stars!