I am broadly talking about most open software I've used (not specificallyaiming at Libre office of open office), yes the user interface tends to be shit. Open software tends to be written by programmers and not users of that type of software... this is part of UI but for some software it's far deeper than that. There's a disjointed clunkiness of how a user of that software would expect for the program to be laid out that is missing from far too many open software.
And I've repeatedly heard terms like "freedom" to describe open software, but what does that even mean when they typically don't handle common filetypes all that well. Let's stop pretending that anyone uses ODT. So I have the freedom to not be able to open up a Word or Excel or PowerPoint file and know that the file will come in perfectly fine? Or I have the freedom to save out a file created in Open Office and know it will appear exactly the same way when a colleague opens it in MS Office? We both know there will always be issues making that transition so I wouldn't exactly feel all that "free" if I was using OO in a work environment.