I manage an Anime Forum (Spanish), I check the Categories, and the only category that applies is on the International Sites. Not so good to promo my forum I'll be on a generic category.
My mobile users are about the 0.02% of the forum traffic, is pretty low. The app, looks great, and maybe I could get a trial when Apple approves the app.
Is a hard decision:
App. only for iPhone ($80/year) vs a skin for all mobile browsers ($200/unique + 10 per upgrade).
I'll watch the app evolution and of course the site.