[bdeshi]

If you meant the splash screen when it starts up, this can be turned off in the settings.

Otherwise the core app's UI looks fine to me personally, though some of the plugins make some, unusual, choices.

[stavros]

The UI is a mess of buttons and menus strewn about everywhere. I'm not complaining, Calibre is a great project, but let's not kid ourselves that the UI is even mediocre.