I love Porcupine Tree. Personally, I can't get past the growling of the Opeth vocalist but I've listened to enough of their music that I hear why, if you like that vocal style, people enjoy them. Do check out Steven Wilson's solo records too. (He's the leader of Porcupine Tree.) Another good Neo prog group is Spock's Beard, especially their first 5 albums. Another recommendation is The Flower Kings from Sweden, although, like Opeth, their vocals can be an acquired taste. Happy listening!
Spock's Beard and The Neal Morse Band are a couple of my favorites in the Genre, I pretty much have their entire catalog(s)...