I've been a bitbucket user for about a year, switch over from github. One thing that has always bothered me about your service(and one of the very few I might add) is the access management -> user/email address auto complete. It's very difficult to find the user because often I know the first name last name but not the actual username. Typing in the users F L name does not auto complete the user correct or even come close. This makes it difficult to add users to the repo access.
Personally I think the autocomplete should provide a dropdown of all users that are currently have access to any of your repos. First Name/Last name search also needs to improve. Or maybe just a page with a list of users along with their username for the account? IDK, but I do know what you've got there doesn't work too well.