I have no trouble playing either way really.. I remember years ago I did have trouble playing while standing.. but yeh.. I don't even think about it any more.. If I have the choice, I will stand because it allows me to walk around on stage and talk to the other band members while I am playing if I need to communicate something.. like "my string just broke".. or something equally as important.

Anyway yeh.. even in a studio situation, I would still stand.. I feel more energetic as well.. anyway..