Haha ya the tunnel vision is pretty trippy, especially after playing a really long song on Expert a few times till you beat it without a break, then you look at like the wall and it looks like it's all moving haha
But ya, back on topic - The first day i played, i played for like 7 hours straight on easy then medium after a couple hours...
the second day all i did was complain about my hand hurting (it was my excuse for losing on a song heh)..
then either the second or third day i beat the game on medium
by the 4th day my hand didn't really ever hurt...
so i guess you just have to build up the muscles in your pinky finger...
cuz going from medium to hard and expert with having to use the pinky a lot more and moving the whole hand back and forth for some parts, my hand was like, "WTF IS THIS? I'm not supposed to be moving my pinky this much for anything! This sucks! I hate you!", and it got revenge by causing a lot of pain lol
So basically... the more you play the less you'll notice it, and the better you'll get because you'll be used to hitting those fast notes with your pinky and such
just takes a lot of time getting used to