There was a bizarre article in the New Yorker about how the journalist writing it sat behind Sondheim when he saw FUN HOME downtown. It really was meaningless tripe, because aside from hearing SS grunt a few times in what was assumed to be pleasure, the journalist really didn't know what Sondheim thought.
And he did a beautiful job with Addison and his boyfriend in ROAD SHOW, as PalJoey points out. Aside from that ballad already mentioned, "You" is rhapsodic as well.
I'm sure Sondheim at least appreciated the show. He championed Tesori's VIOLET some years back when it was at Playwrights Horizons.