Most people don't realize, but most good native apps (not games) are only available on one platform. Only big companies and funded startups has apps on all platforms that are good.
Also, major problem with Phonegap is jQuery mobile and similar frameworks. they are heavy and makes app sluggish.
Android specially chrome browser is another major problem.
Despite all that, you can still create a very good app that performs well on all platforms.
I wrote this hacker news HTML5 app mainly for trial run to see if it is comparable to native apps. I only developed and tested on mobile chrome, ios and desktop browsers. r/windowsphone redditors told me it works pretty good on WP8 too.
What I have learned? - Android (chrome too), Firefox and Window Phone 8 - they need to provide better support for overflow scrolling. - iOS - Remove 300ms delay for click for mobile apps - WP8 - You can't fucking embed fonts in your phonegap app. It has to be hosted on remote server. Also you can't have ? in local urls (files that you are loading locally). It won't load those files.