Rethinking the user interface

Hi everyone,

I'm new here. I've been using Calibre for more than a year to convert ebooks to my iPad. Now that my parents have a Kindle, I am teaching them how to use Calibre to add ebooks from other stores. However, thinking as them, the user interface is really really complicated. And it shouldn't be.

I have seen other attempts to improve the UX & UI of Calibre that have gone nowhere. So I'm not going to make a wireframe of what I think it should do. Or at least not yet.

First, I want to know what you use from Calibre, how you use it. It has many options, many buttons, many filters. But, what do you use? What's your primary use? How do you send your books to your ebook device? Do you edit the info of the book? How many books do you have on your library? Do you have one or several libraries?

With all your answers, we may work on a new interface than can go somewhere. Right now I see 40 buttons/filters/elements in the default view Calibre. I'm sure 90% of the people only use 3 (add book, convert book, send book to device).

So how do you use it? what do you use?