How re-usable is it really? The bulk of the work is being done at the server in this case, and the app is mostly UI code. UI code is very platform dependant. I think that HTML5 is probably the future, particularly if things like Firefox OS take off, and it's probably fine for a MVP mobile app (possibly combined with something like PhoneGap). Currently though, native apps definitely provide a better experience, and you should probably do it if you have the resources... and this is from someone who really enjoys web dev and dislikes iOS dev.