Somehow, the gentleness didn't surprise him as much as he would have expected. He met the kiss softly, tears pricking and threatening to overwhelm him. He was glad John pulled back when he did. He just stood there for a long moment with his eyes closed, breathing slowly and with only a slight hitch.
Then he opened his eyes. "Thank you," he said softly. And did a fairly good attempt at a grin. "Come on. TARDIS!"