I did ship a complex HTML5 Offline app for a client, and it was more pain than it should've been, but I made it work. (Tip: the two big mobile platform owners seem to have an obvious disincentive for HTML5 Offline to work well.) If I do something Web-first, it'll be handheld&desktop responsive, and I'll be keeping a smooth path to HTML5 Offline in mind as a possible alternative to the app stores.