The chapter forward/back buttons were of most use for:
1) repositioning to the start of the chapter to recap something one missed out on, or just to set up for next listening session. Now you have to use the scrubber or chapter list to do this.
2) skipping to the next 'article' with NYT or WSJ daily digest (but I typically use double click on my headset play/pause button for that).
The bigger buttons are okay, but they tend to cover up the 'cover' art, including the title. It's weird that it doesn't display the title of the book anywhere, and the 'info' page doesn't necessarily help with that: the font is too big and the title is usually 'compressed' ('The Picture of Do...ray (Unabridged)').
I agree about chapter list, it should report where you are in the current chapter, if not give you a way to navigate within it.
Not sure what you mean by additional reading speed options. Is 2.5x new? 2x is about as much as I can handle for most narrators. I'd be more interested in 1.25x (Android has this) or 1.75x.
Bookmarks are somewhat more useful with 'whispersync for voice' titles. You can create bookmarks or annotations in the ebook and these serve as navigation points in the audiobook. For some reason highlights don't sync: it would be neat if that text were copied over to the audiobook. With annotations, you could type in chapter titles (with a bit of work) so you have those available in the audiobook. But of course not all titles are W4V.