I'm pretty descent on Rock Band while sober, but after 5 or 6 shots of vodka and I'm the motherfucking king. The first time I noticed this is when I was completely hammered at a friends house and her little brother challenged me to Guitar Hero. I ended up five-starring Jordan on Expert, shocking both me and everyone in the room. Sadly, I've never been able to replicate the results with Jordan, but I've managed to do this with almost all of the Rock Band 1/2 tracks.
I've also noticed that I play better while upside-down, but I'd never combine the two.