At the moment, not a lot I must confess :) We're still in MVP, and learning a lot as we go on what features are important.
Currently planned: Integrations with source control (GitHub, BitBucket etc), the ability to pull in contextual data from third party apps (Sentry, HoneyBadger), the ability to escalate tickets from support to the dev team from Zendesk, Uservoice etc. Plus support for more dev focussed workflows, planning, reporting etc
Yeah definitely, we used Pivotal Tracker for a long time ourselves. There's a lot to be gained, particularly from a scheduling and reporting perspective, by having estimates but without the strict sprints of Pivotal.
not exactly estimating, but I built something to let the team vote on items in a Trello list. We usually vote more along the lines of "bang for the buck" ie importance/estimation http://blog.forcerank.it/tame-your-trello-backlog
Currently planned: Integrations with source control (GitHub, BitBucket etc), the ability to pull in contextual data from third party apps (Sentry, HoneyBadger), the ability to escalate tickets from support to the dev team from Zendesk, Uservoice etc. Plus support for more dev focussed workflows, planning, reporting etc