I've now been using this app for quite a while now and can say that this is the only app so far for Android that actually appears to understand what a stylesheet is and what to do with it.
All my formatting gets displayed, be it just italics or bold, all the way to small caps and beyond. No other ereader on Android does this so well, version 1 of Aldiko came close but ever since version 2 it's been pretty rubbish.
I've also tried Moon+, Cool Reader, FBReader and Kobo Reader and none of them handle as much of the CSS as this app. None of them even look close to what was originaly intended to be displayed, only Mantano seems to.
Also every single ePub correctly displays the cover image in the library view and all the authors are also listed, this isn't somthing I find to be true with Aldiko or Kobo.
One thing though I would like to see is for the toc to give be some indication of what chapter I'm currently in. Just a tick next to that heading would be sufficient like what I get with Kobo and Aldiko.
Also with Kobo it tell me along the bottom of the screen which chapter I'm in as well.
Note: I've not compared this to Kindle due to it uses a different file format, all the above comments are for ePub readers.