According to me -30% Bounce rate is Good. In fact lesser the bounce rate you have,The higher page views you will get.
Well, not all bounce rate are bad. It will depend on what kind of site it is. For example, a bounce rate for a certain portal site might not be a total bad bounce rate at all.
According to my opinion, if the bounce rate is below 50% then it will be better. But if it crosses 50% then you have to work on it to reduce it.