It has eight zillion features, all of them overlapping. It has so many fields, dimensions, views, and reports that I despair of ever getting a setup that usefully matches an actual workflow. The point of a work tracking system is to bring everybody together, but I regularly see people dealing with Jira by having their own separate tracking methods: docs, emails, spreadsheets, sticky notes on the wall.
I like Trello better because it's more straightforward. Less complexity means less chaos and an easier time getting a workflow representation that matches actual workflow.
But personally, I like things that are more straightforward still. E.g., my last company ran almost entirely on index cards, and we were very happy with that:
