Having never heard an Opeth song in my life, I have to say I was eagerly looking forward to this as I have heard good things about them. I was very pleasantly surprised.
The song is very long, nearing 11 minutes. But it keeps it interesting the whole way through. The songs riffs constantly change and move around, keeping your fingers interested and brain working.
It also comes with two solos, the first one being really short and quite easy, and the second one is really fun. You've got fast sweeps, and tricky finger placement to keep you on your toes.
There are also some cool acoustic sections during the quiet parts that move around a lot, and mix in some chords as well.
The song itself is beautiful, a good mix of growling, combined with an alt metal twist and good prog drumming makes it a neat song to listen to. If any more Opeth was released I would hop on it in an instant.