My team tried it several times over the first 1 - 2 years it was out. I have not tried it recently. That said, at that time, we could never get it to stick. It was good for high level stuff, but like all project management software, we ended up constantly working to keep it in sync with reality. This was especially acute when using github because for any stuff that was code-related, we were basically duplicating tickets and tracking in both places. So github tickets were the real source of truth and Trello always lagged. Once that happens, the non-code milestones start to suffer as you start wondering why you're doing all this in the first place.

Tracking issues in github (and we use FogBugz as well) has the benefit of being where the "rubber meets the road", so it's effortless and transparent to keep up to date. Merging non-code tasks (e.g. design work) with code is still something we struggle to track and keep tabs on.