I think my sadness on the Doctor's behalf on being alone again was overshadowed by how happy/proud I was for his Children of Time for growing up and moving on with their lives. If you see Sarah Jane at the end of "School Reunion" and compare it to how she is at the end of this episode, the life she's made for herself outside of the Doctor is quite lovely.

Same goes for Jack, really. He didn't even pause to think about staying with the Doctor since he'd promised Gwen and Ianto he'd be coming back.