@Ronald - Good to hear, thanks!
I do have another question. Am I correct AEC adds two queries per comment? Weird thing is, on one of our really popular posts (contest post) we have over 800 queries. With AEC enabled this translates into
1704 queries. 6.600 seconds.
If I deactivate AEC, I only have 46 queries on the same post ... Ofcourse, this really hurts performance, especially on posts where we have over 50 comments (happens more often than not).

Problem is - like I said before - we can't uninstall this plugin as our users would come lynching me ;) Is there a way to completely prevent AEC from executing at all when comments are closed? (we automatically close all posts after three months). This would already help tremendously.