1) End users are not the buyer. It's the Head of Delivery, Iteration Managers, Agile Consultants etc that are. For them JIRA is great because it's heavily customisable and scales across the enterprise. It's actually quite hard to balance this with a great end user experience.

2) They are in the middle of a complete UI rewrite and I've only briefly used it but it's definitely much better than the previous versions. I imagine the Trello acquisition is also going to help them here.