I've really been enjoying developing an app with Phonegap and Sencha Touch. Sencha Touch has a pretty steep learning curve, but once you get it, its pretty nice and you can put together a cross platform app REALLY quickly.
I plan on using Phonegap + Sencha touch to release first iterations of apps. If the app looks like it is picking up steam in either the iOS or Android markets, then I can decide to invest the time in making a native version.