My co-worker and all-around good guy, Rob Rhyne has officially open sourced Briefs.app as of today. After three months of being dicked around by Apple's review team, he's finally given up on getting Briefs.app onto the App Store.
Throughout the ordeal, Rob has taken the whole thing with tremendous grace and has only good things to say about the people involved in the entire process. I hope he'll forgive me for not being quite so gracious.
I can't see anyone making a business case (i.e. is an non-indie developer willing to take the risk) for a iPhone app.
They come with both known unknowns and unknown unknowns.