For me, it wasn't the "darkness" of Poetry that made me not like it as much as the previous albums - I like darkness and am totally fine with it. I just found most of the songs to be kind of boring save for Great Pandemonium, Once Upon a Time and perhaps Hunter's Season. It might've been the experimental nature of the album, I think. I'm a sucker for Seventh Wonder-style epic and melodic vocal lines which Silverthorn has more of than PFTP which is why I'm enjoying it more. Now, I have very little musical knowledge so it's all a matter of personal tastes for me, technicality and production and all that stuff aside.
@ZGoten: It's interesting that you like Sacrimony more than other tracks on the album, since a lot of the reviews and reactions I've read say that the others were better. It might be because I've been listening to Sacrimony so much already that I don't feel it too much any more
My favourites from the album have to be Song for Jolee and Prodigal Son so far.