It's probably a case issue. Make sure that you're using "buttonStyle" (lowercase b, uppercase S, and no space). If that still doesn't work, let us know.
We're probably going to change it to be case insensitive in a future release because this problem comes up every once in a while. We don't mean to make it inconvenient, but we always want to make sure we don't mis-interpret what someone may be trying to do..
Hope that helps, but if that's not the issue and still doesn't work, let us know and we'll come up with an even better, and cooler solution!