After first reading your request, I wasn't sure that there would be that big of a difference between Mac and Windows versions of PE, but then I remembered reading that the Organizer was not present in the Mac version. That said, the only other difference I would imagine (and I'm sure others will correct me if I'm wrong) is that the keyboard shortcuts would be a bit different--but aren't we all already used to that?
That being said, I saw what you mean... a few people reviewing books online noted that they were written more towards Windows users, but they never said it made the books unusable. In fact, many reviewers gave high marks to some of the books while noting that keyboard shortcuts had to be modified and entire chapers (ie those about Organizer) could be omitted. You might also want to note that some noted that the only big difference between these current books and previous versions was info about Organizer, so you might be able to save money and buy an old version.
One that I saw that seemed to be pretty well received was "The Photoshop Elements 3 Book for Digital Photographers" by Scott Kelby. It apparently does have the limitations previously mentioned, but does reportedly give Mac keyboard shortcuts.
Good luck finding something to meet your needs.
