Ventajas
"Allways In-Store" I think it was.
It depends on where they send you, but the people that work at whatever store they send you to can be really nice, even the manager. :3 Good for getting some fresh air, talking to people, and overall a good place to start.
Personal note: If you promote enough times at a store you regularly shop at, you'll have an easier time finding what you need in the future.
Desventajas
It could be for the sake of the company, but from experience, some of the coordinators like to play favorites with their demonstrators. Calling these coordinators unreliable is an understatement. It could also be the fact that they just recently lost Safeway. On top of that, they might tell you about a new rule of code that seems strange and possibly frivolous, so be VERY thorough if you're reading up on company policy and/or code of conduct. Don't let them confuse and possibly make you lose out.
Personal note: The managers at (most) of the stores I worked at were a good bit more forgiving (and nicer) than the ones at the company.