He doesn't HAVE to be, but he is. Isn't that a good thing?

> It could be that while a small number of users are helped by his personal attention on the forum, a much larger number of users are left frustrated by the UI.

This is just speculation. Without data to back it up, I can say the reverse is true too.

Since there isn't a large number of users that are posting about how terrible the UI is(on the Calibre forum), it's probably functional enough and people can navigate it.