I have mixed feelings about this episode. While it's not magnificently excellent, it is in no way awful. It's just....pretty good. I just think for the most part, it could've been made better, and it really needed that extra something for dealing with such a difficult, tender subject like what they dealt with here.
This episode was quite an emotional, heartwarming, feel-good episode. Bart losing his best friend in the world, and then making best friends with his sister. Then Milhouse returns, leaving Lisa feeling sad. But Bart didn't forget their relationship. I found that rather pleasing.
Now the ending was a bit of a letdown. It was leading on to a climax of a mainly emotional episode, but then this silly, unfunny scene came along and ruined the feeling and vibe this episode seemed to be giving out in the first place. It's not the absolute worst ending of an episode I've ever seen, but it just REALLY did not need to be included.