The folks at Barnes and Noble aren't giving in to Amazon just yet. In fact they've already issued an update of their Nook for Android app, adding some lovely new features. These include 4 themes (day, night, sepia and butter), new margin settings and brightness options and the ability to read non-DRM ePUB books (yes!). If you have an Android 2.2 device (HTC EVO 4G and Nexus One are the likely candidates), you can store your books on a microSD card rather than internal storage.
B&N says updated iOS apps for the iPhone, iPad and iPod Touch will be coming later this month.
Our Nook review: http://www.mobiletechreview.com/gadgets/nook.htm