I haven't published my books yet. I have some calendars for sale on Lulu.com and my children have books for sale as both ebooks and print books in the book shop there.
I am planning on using Amazon for my books which will be available as traditionally printed books and Kindle books. Amazon has the widest distribution of all of the different self-publishing firms I have checke dout so far, and the cost is minimal. However, I will only use them if I decide to go the self-publishing route. I haven't decided yet whether I want to go the traditional publishing route or not yet.
I may have to when it comes to my children's picture books, but that is because I have no skill at all when it comes to drawing and am not capable of illustrating my own books. I tried to teach myself to draw, but the best I was able to do just wasn't good enough for the way I want my picture books represented. You can see my attempts at drawing on Designing Doodles. I still have fun trying to draw though.