Currently using RT3 (Score 1)

Not too long ago we migrated from sourceforge to RT3; the SF VM died and we were already in the process of migrating from prebuilt VMWare services to natively hosted stuff. SF is unfortunately no longer (maybe it never was) available as a project in this fashion, and we were only using it for the tracker.

RT3 is a pretty decent system, but the interface is rather complicated and cluttered, and modifying it is not as easy a task as one might expect. For example, "resolved" items do not show up in any listings by default, and making custom listings or modifying existing ones can be painful, so we are instead using a 'resolved' queue and never actually resolving issues "the RT way."

I have taken another look at Mantis and it looks like it does everything we need and isn't overly complicated, so I've put up a copy for evaluation by management.

Mantis claims to have integration with subversion built in, but even if it doesn't, it's really easy to use the subversion commit hooks to do some form of integration yourself.