I obviously don't know as much about Porcupine Tree as DR D B SILLARS (below). I'm a reasonably new fan of this awesome British band.
I was first introduced to them when my younger brother told me about them after seeing them support Dream Theater a few years back. I downloaded a few tracks to see if I'd like them and then bought The Sky Moves Sideways. I liked it well enough, but haven't played it that much. Then I heard Deadwing, which totally blew me away. I'd bought Deadwing and In Abstentia; both of them the DTS versions.
I listened to them almost constantly and still listen to them often.
I decided to check out a few more albums and got Signify [Remastered] Up The Downstair [remastered]. After reading the above review I'm quite glad that I got into them when I did. I'm a drummer myself and am not keen on drum machines, although nowadays you can sample real accoustic kits and play them through a keyboard or whatever you like; but that's by and by.
Since rediscovering Porcupine Tree I haven't found a single song that I don't like and very few that don't move me in some way.
A month or two ago I would've put Dream Theater at the top of my favourite bands list. I think Porcupine Tree just took the top spot and I can't see them being knocked off anytime soon.
Porcupine Tree are deep, progressive, atmospheric and inspirational.
An album of superb quality.