We're currently evaluating Jira, Greenhopper, Fisheye and Cruicible for our company and so far I have yet to see the value of Fisheye. AFICT, it basically mimics everything Mercurial already does. Please correct me if I'm wrong here, but from what I've seen, so far, there is no real linkage to Issues - UNLESS - the committer happens to mention the Issue ID in his/her commit comment.
If that is indeed the case, then isn't there a cheeper way to have Jira interact with Mercurial directly?
Sorry for sounding negative, but we're on a tight budget and need to justify every penny we spend...:-(