Anybody has a feeling how much effort it would be to replace the webkit engine with firefox in Android for webview rendering? I am quite unhappy with the webkit engine on so
Non-trivially difficult. Depending on how much consistency you need between your new WebView implementation and the existing implementation you could have a lot of work to do. There is an existing Firefox browser on Android so you could start with that (which would hopefully save you a lot of time) but at the very least you would need to check that the Firefox libraries exist and are accessible, you would probably need to bundle them with your app to get them to work (which would massively increase the size of your app) and then hooking up all the WebView apis would involve a lot of work.