I loved the set up for Martha and Mickey to join Torchwood next season (if the rumors are true).
Rose and the Doctor (well clone doctor) live happily ever after (at least for now)
Seeing K-9 special appearance was awesome.
And I have to say that Catherine Tate (Donna) was MAGNIFIGENT!!! I didn't really like her in the Christmas special but when they brought her onto the series she changed and turned into one of my favorite companions of all. Her acting is brilliant and she got to shine in many of season four episodes. And what happened to her in this episode was heart wrenching. She's the woman that saved the universe and when the Doctor took her back to live with her family and removed the memories I thought..okay at least she's not dead. But then I remembered her life on Earth and her unsporting mother who makes her believe she is nothing and worthless and it makes me sad. Donna is so much more and it might have been better if she had died the woman she was rather then go back to the woman she use to be. I just hope all the crazy experience that Donna's mom had will change her mind about her daughter and she'll give her encouragement and respect as she deserves.
Anyways.. a wonderful ending to a wonderful season.. this is a must buy when it comes out on DVD.