Guess it's a random thing as to whether one gets an ePUB book, I could go broke buying 'em just to try to get one
The IREX doesn't yet support B&N ePUB- that's supposed to be coming in the April firmware I posted about.
My review on MobileTechReview pretty much covers everything that did and didn't work for me. There was nothing wrong with the PDB books themselves as far as I can tell, but the IREX could support more features when working with that format (like adding the find word feature supported in other formats). In fact, so could the nook! For example, the nook has 3 fonts but you can't change fonts in a PDB book. eReader/Peanut Press books work equally as well (or not well) on these readers.
Personally, I prefer ePUB-- it's well supported by a variety of readers, seems easier to parse and one gets the full set of reader features with ePUB vs. PDB.