I've been doing mobile development for the last fifteen years, and my experience with PhoneGap about three years ago was the most ridiculous and painful experience of my career.
Developing with HTML and JavaScript is a pointless chore. It is literally easier to learn both iOS and Android programming and write the same app twice than to put up with and hack around the stupid limitations of hosted web apps. You lose nothing but the ability to write once and debug everywhere shared code, and you gain native performance, native look and feel, and you can use two vastly superior programming languages. Your code can execute in background threads, and you can use a real debugger and whatever IDE you prefer.
That doesn't mean you can't write decent apps using HTML and JavaScript. But be honest. When you use one, you're not actually impressed by what you see. You're impressed the same way you're impressed when you see a demo written for the C64. The accomplishment is not what it does, but what it does given the severe limitations of the platform.