If so, I can't figure out how to do it. I wasn't able to buy a fractional share and then bought a full BTC. Now I wanted to just sell half of it, but it won't let me do that either. Is this just the way it's set up or am I don't something wrong? Thanks.
Yeah, I do it all the time. I'm a pretty poor college student, but I always try to keep some fiat on Gox in case trade rates are good. All I do is fill in the box that says "total amount to spend in USD".