Well, mine arrived today, about 4 hours ago.
I've been spending most of that time formatting and reformatting using Calibre, and using different original files (public domain books only, so far). Problems still exist between the originals, Calibre, Astak, and what I actually would prefer. So far, it seems to me that ePub is better for me than Mobi, but that may change some day (maybe even today).
But then again, I'm a nerd, so I have what it takes to experiment with every option until I get the desired results. Also because I'm a nerd, I prefer to use Calibre's command-line options to (re-)format, and I also prefer my own folder structures (which may very well vary from one series or author to another).
I haven't had to open the user manual yet, as everything I've done on it so far I've read here at MR.