As fast as the web is now, I'm no-longer a fan of pressuring browser developers on performance. What we really need is to improve browser interoperability.
Rendering engines are constantly adding support for awesome new features... but those features can't really be used until all the other browsers decide to implement the same feature - which tends to be years later. I'm a huge fan of the "Interop" project, which maintains a list of web technologies everyone agrees should be cross platform and pressures rendering engines to implement those features. The list of features changes every year.