OK, I'm going to play Devils Advocate here. I loved The Crane Wife, and think the only song that isn't worth a damn on it was Shankhill Butchers, but I've started to notice a few things about it.
While the structure of their songs is quite interesting and varied, the actual makeup of the various sections on the longer songs especially, such as The Island, basically involves just riffing over and over again. Nothing new or interesting is added until they have kind of run the section into the ground, at which point they change tack, and start all over again. I find sometimes that I wish they had moved onto the next section just maybe a few bars earlier, to really nail the song. I had this exact same problem with the Tain as well.
I just really don't think that song, or the entire album is as "progressive" as people are making it out to be, and while I still love it, I would not be particularly concerned that others felt differently. I don't think the keyboard sound they have in The Island for the 70s retro throwback sound, or the two rather long songs are enough to qualify it.
And I do not want people to think I am a Tain hater either. When I first saw it, I kind of squealed at the prospect of sections partitioned off by Roman Numerals, with 2112 and The Complete Trip coming to mind.