The look & feel argument is total bullshit at least for me. Every native app I am using is completely different. The only consistent look & feel is with ms office apps like excel, word and powerpoint.
Performance is also a lot about how and who wrote the app rather than if the app is native. It's just harder and requires a lot of knowledge to make javascript app perform well, but it's not some impossibility.
And yes, standards are still creating too high level APIs and it takes forever to gain more and more access to the same things native apps have. But that will get better due to extensible web manifesto.