One of the worst things i see, is local bands around where I live, with guitarists with their guitar so low, they have to bend over, just so that they can hit the strings with their pick. My advice for playing standing up, is defy what you think looks cool, which sounds a lot like what others on here are saying. I used to not be able to solo standing up, but i fooled around with my strap for a while, and I'm almost nipple riding it, and can play just as well as when i sit down. It may not look "cool" to others, but functionality before fashion I guess.