The main app is generally functional, but it's easy to see the deterioration of the smaller subsystems that large platforms like that need for a good user experience. For instance, I have an account that I am unable to log into because their password recovery/change feature doesn't seem send me anything when I click it. I'm sure frequent users have a litany of little things they've noticed that are flaky or outright broken, even if they can still send and read tweets.