I used it (Jira) for a short period of time a while back. I seem to recall that it's performance was highly influenced by non-obvious JVM parameters, and bits of the system would stall or crash without a clear pattern until a bit of trial & error with parameters solved it. It wasn't very "turn key" and the out-of-the-box config were... less than ideal. This was for a single user (me) so it's not like there was a much of a resource crunch.