Thinking about the question: "what do you struggle with most when it comes to self publishing?" The more I ponder this, the more I realize he's not asking about the editing or marketing, it's about formatting.
I've self published two works. Both in ebook formats and both in print. With ebooks I've struggled with getting an active TOC to function. With print books, the wrestling match has been about getting the page numbers to start at the right place. I'm also challenged to find away to get rid of the occasional blank page, or one sentence page, created by chapter breaks. Lurking in the forums, I think the first two problems are common with self published works.
I'll probably re-struggle with these issues in a couple of months when I jump into the process again. Perhaps this time I'll take some notes on what worked and what didn't!