I don't understand what you are asking.
Legacy bugs are bugs from previous versions. All Altium is saying is that they've tried to fix all of the bugs from earlier versions before Summer 09.
It doesn't mean that there are no bugs in Summer 09. They created new ones when they added a bunch of new features such as doubling the number of available mechanical layers, supplier data, a new licensing system, colored nets, fab and assembly testpoint improvements, a new way of displaying DRC errors, faster DirectX displays, etc.
With new features there are always new bugs. However, this version went through seven beta versions before release to make it as clean as possible.