No file formats have been mentioned yet. A rep from B&N recently said "We believe readers should have access to books in their digital library from any device, anywhere and anytime," which makes me hopeful they will support a variety of formats.
Source: http://www.itpro.co.uk/616102/barnes-noble-to-sell-kindle-rival
It is indeed
Nook, as nook.com is registered by B&N, although still not active yet.
http://whois.domaintools.com/nook.com