Porcupine Tree are a great prog band. I'm a huge Rush fan and have always liked Yes and not very long ago my brother turned me on to PT. I'm very glad he did, we are both anxiously looking forward to the release of "The Incident"
I can definitely see Dark Side of The Moon in here. As far as albums go, I think this one has the most interesting (and coherent) concept. As a journey it reminds me of reading 1984. It's pretty damn awesome.
I agree with vwbus1979 that Signify embodies a solidarity of sound and concept that PT has failed to create before or since. As with vwbus1979, this was also the first album through which I discovered PT, and the mood and flow of the album certainly did evoke images of Dark Side of the Moon, though with more of a modern sensibility. The analog atmospherics are lush, and the songwriting is more cohesive and satisfying, as a whole, than that featured on any other PT album.
This is the "Dark Side of the Moon" album for me. This was the first album I started listening too and the most well thought out album in the catalogue. I do appreciate all of the other albums but this one is the most stable Porcupine Tree out there...