I've gotten good enough at the guitar and bass that I can usually finish most of the songs in Beatles Rock Band on easy with a 100% score, even the more difficult ones like Birthday or Revolution. So I tried playing Lucy In the Sky With Diamonds on medium.  I actually managed to get a 97% on it.  (In Rock Band, the easy level only uses 3 chords, medium uses 4, while hard and expert use all 5 chord buttons, requiring you to move your hand up and down the fret.  There are also more notes to play as the difficulty increases.)  I found my fingers working on their own at times, managing to hit notes that my brain totally missed.

Playing Beatles Rock Band has really increased my appreciation of their music.  You begin to see patterns and eccentricities in the music, such as notes that are deliberately out of beat.  Playing the bass is especially insightful since you don't normally pay much attention to the bass player when you're just listening to the music.

I've got blisters on my fingers!