The release of Gnash 0.8.8 brings various improvements to rendering, ActionScript execution, compatibility, and flexibility.
But the most significant change is more of a removal than an addition: Gnash no longer has any AVM2 code. AVM2, the ActionScript Virtual Machine introduced in the Flash player 9, is increasingly used in new Flash movies.
It was becoming clear that the original implementation (started in about 2006) of the newer ActionScript Virtual Machine was fundamentally flawed. So fundamentally that it was obstructing code for the old virtual machine without any benefit to Gnash at all.