I liked it; but I'm not sure why or how this has picked up a theme of being an alternate ending an all. Without dropping spoilers for Angel Beats; this is clearly just what happened after the season finale; and before the credits. No one has any idea how long a time span went from the end of the show and the ending credits, so it seems pretty obvious this is just a glimpse of what happened in between the two points.
Seems like it could be a preview to a season two that at least at this time never came out. That's about it. A two minute short. I enjoyed it, but there was nothing big about it. I liked it for what it was.