I'm a developer at Clarity and we use PhoneGap to publish our native iOS application to the App Store.

From experience, wrapping our website in PhoneGap has been a really good way to get a native application that has native features like push notifications for "cheap".

The nature of Clarity itself requires you to be online to use the product: browse and search, request calls, ask questions, etc. For that reason, we never looked at providing offline support. If we can't find an internet connection, we show a very simple alert dialog.

Another concern that we had is startup performance, especially on subsequent starts. To remedy that we added a simple caching layer to the native code that allows us to save our biggest assets (JavaScript and CSS) locally and avoid having to re-fetch them unless they changed locally.