Use old version of flash, I am using cs 4 and it works well. Because it is vector, you do not necessarily need bones or motion graph, a lot can be done with frame to frame animation.
Animestudio has one big problem, its locked bones creates jerking effect. That is why I moved back to flash, not sure they have fixed that now.
Spriter also has some jerks, as I was testing it right now, but it can be smoothed out.
Anyways you have to get a vector software, because spriter is not a design tool and trust me if someone has learned flash or illustrator, they will never go back to inckscape or other vector software, which are no where in comparison.
Spriter is looking good to me and affordable for now, but it will take me a week or more to completely test it.