We used Redmine for a while, but never got the Ruby stack to perform good (we are a PHP shop, so..). I remember the insane version dependencies ("redmine revision x to y needs package P in revision a to b") and that it seemed to stagnate in its development.
In the end I'm happy we ditched it in favor of Trello.
Love Trello. I'd like a locally installable version of that integrated with something like Gitlab (maybe this already exists, I haven't bothered to look).
It always seemed a bit slow to me as well. The dependencies issue may be fixed with modern usage of rvm-/rbenv-type things, but I haven't messed with Redmine for a couple years. It's funny you mention the pace of development too; the community actually forked at once point [1], I believe due to frustration with how the development community was being handled. That fork is dead now though.
In the end I'm happy we ditched it in favor of Trello.