What are you guys using to sync the app? I am creating an app as well and thinking of going with Chrome Package App.
The way to do a desktop app using web technologies that feels more "real" is with node-webkit: https://github.com/rogerwang/node-webkit
We did this project in collaboration with Google, and they were great. We wouldn't have done it at all otherwise. But, I still do want to create a node-webkit app, because I think that's what users want, a normal app, not some weird hybrid thing.