1 You don't need to watch the second series to understand the movie. I haven't watched it, and it's been since the original release that I watched the first series, but I had no trouble with the movie when it came out.

2 If you really remember the first season well you don't need to watch the second season to understand the movie. But the second season can still help.

The Tanabata episode (a.k.a. "The Only Good Episode") is really the key to the whole series. There are some references to it in the first season but it's helpful to watch the real thing.

If you can force yourself to sit through "Endless Eight" you will really be able to appreciate what motivates Yuki.

3 I'm half-way through Endless Eight.  I quite like it for what it is, but my God that must have been annoying to watch week-to-week.  The way they reshuffled season one for broadcast was a stroke of genius, but this would have been a bit much even for me.

4 I loved Endless 8 as it was airing, and I still like it now.  I'm still annoyed at people who trash it without having actually WATCHED the episodes, but whatev'.

5 Having seen it all now, I think the Endless Eight sequence was handled very well, but between that and the five-episode making-of sequence, it meant that there wasn't much story in season two.

If they'd compressed Endless Eight to four episodes (it can't really be done in less time than that) and making-of to three, plus the Tanabata episode, that would have left six episodes for the Disappearance arc.  That would have been a really strong season two, with a nice mix of new story and back story.  But of course then we wouldn't have gotten the movie that we did in our timeline.

And Jonathan, you're right, you really need to watch Endless Eight (I think all of season two) to get the full impact of the movie.  Everyone else has had eight months of Haruhi; Yuki has had nearly 600 years.

6 Wonderduck, I agree with you about the way KyoAni handled the Endless Eight arc.  Every chance they had to be lazy and re-use animation from the previous loop they avoided.

And I only noticed now that one of your commenters signed his message as John Smith.