Apart than the fact that the editors were not native English speakers and I had to spend quite a bit of time reverting several of their editing changes, the whole process was generally smooth and distraction-free (although note I haven't really written a book before so I can't really compare to other publishers) with a few exceptions:

1) Depending on the editor team assigned to your book, they may introduce arbitrary content guidelines (e.g. no code blocks over 15 lines, no figure subtitles; had to press hard to get them restored etc.) after you have already submitted a couple of chapters. I don't really mind the guidelines but it would be great to know them in advance as I had to go back and revise the content.

2) My biggest gripe was their authoring workflow. Personally, I would prefer to write everything in Tex but unfortunately, you need to use their online editing environment (essentially, a wordpress installation with a heavily modified tinyMCE). As I do everything in vim nowadays, I had to setup my own workflow (write markdown + bibtex references, pass through pandoc to convert to html, run a sed script to inject the correct css styles and copy the result back to their system). It's a bit more effort but it allowed me to work offline and use git to track my changes. If anyone is interested in a similar setup, let me know and I can push a repo on GH with the Makefile/css scripts.

Also, there doesn't seem to be a way to get an estimate of the book sales unless you wait for their periodic royalties report. Not sure how it works yet because the book just got released but maybe someone else can comment on this.