Charging users to use your site in anyway, outside of subscriptions or donations, just seems wrong to me.Kier, do not see the white iPhone app as something important for our users. Most likely, your mobile style may be even better!
It is a way for us admins to generate income by having users pay a small fee for this app.
At this point, I'd not even think about it. But you may (!!!) have a presale of this app, bundle it etc. to have some money earlier.