I've been a happy PPS+ user for quite awhile now. I've tried the ebookapplications firmware and liked it but had two gripes...
the first... and most important is that all bold/italics, etc in epub books are gone!
Secondly... it won't recognize any books/bookmarks already on the reader. So even though they say you can switch between the Sony firmware and theirs, it's basically useless because you have to have two copies of your books on the reader (one where Sony needs it and one where ebookapplications needs it) and your bookmarks aren't shared either!