Sarah Jane was always my favorite companion from the first 26 years of Doctor Who, and her return was most welcome. Her story was handled in a very interesting and touching way. I thought this episode was fantastic, and in many wyas highlighted the difference between old and new Who. Never, untill this last couple of years, have we seen the emotional, personal side of the Doctor and his companions. The idea of coming back to an old companion, and seeing her trying to cope with being abandoned by the Doctor is fantastic, and the Doctor's reasoning for abandoning them in the first place is thought provoking, and humanizing.
Was I the only one who got a tad choked up during Tennant and Sladen's last scene in front of the Tardis? I hope not!
All and all, a great episode in what is shaping up to be a spectacular season!