HTML5 can be fast just like Native applications, but you need to know how to make it faster. Hopefully we are going to get more awesome libraries and frameworks like Sencha Touch to make our life easier.
This. It's a lot harder to screw up when using native SDKs vs. the plethora of HTML5 frameworks, some which are more mature than others but none really seem to have a "standardized" way to easily make a performant app in the same way that the native SDKs do.