I think you'd be crazy to abandon a salaried job in the hope of making it big on the app store. I've been working on Dropzone pretty much full-time for almost 5 years now and only now am I starting to see some payoff. I'm wondering whether having multiple apps might be the key to a more sustainable income. Then you can cross sell and hopefully make more money overall.
Relying on Apple to distribute your apps is also very frightening. I feel that policy changes with regards to things like sandboxing could easily put me out of business, and there's no money to speak of to be found from selling outside App Store.
I love writing apps though so I really hope I can continue to do so.