Barring plenty of unexplained, debatable stuff, the episode was a pretty emotional and decent finale to the series.
As someone mentioned, Otonashi's selfish desire to stay in the afterlife with Tenshi can be very polarizing for us audiences, but I personally found that it worked really well in developing his character. The decision makes him much more human in my eyes, and not merely a saint that he was portrayed as during most of the series. His whole life (and afterlife!) had been devoted to helping people, whether it was someone who was stranded in a collaped tunnel or someone who was unable to let go of their grudge against God, he'd do everything within his abilities to save them. But now that his mission is complete (i.e. everyone has already moved on), he's faced with the prospect of eternal happiness with someone he loves, so he decides he wants to be selfish for once. Is that pathetic? Maybe, but Otonashi is allowed to do this because entire existence in this world is due to a flaw in the program. Compared to the Programmer who, in the end, chose to wait indefinitely for his lover, at least Otonashi
was eventually able to let go when Kanade asked for it.
If we're talking about Otonashi confessing his undyling love to Tenshi being sudden though, I'd have to agree with that to an extent. Then again, like Yui/Hinata's marriage thing, there were a good number of hints littered throughout the series that would allude to this ending, so I suppose I don't mind it too much.
Overall, I'd give the episode a 8.8/10, rounded up to a 9/10.
