In my experience so far, getting a full back piece is the best and worst feeling at the same time.
That being said, it's completely 100% totally worth it, and Dave C is going to make your back look insane, @Graeme.
He did an Oni on the back of my right thigh (from ass to back of knee) about a year ago now, and it's the coolest tattoo ever.
Nicest guy too.