I think you'll see a lot of people have success. Some of it will be because the App Store gets so many eyeballs, and some of it will be because people have established customer bases to sell to. But I think its still very possible to be very successful even if you're still building your application. You have to realize, that while some people are having a lot of success just by word of mouth and eyeballs, you can't depend on Apple to do it all. Get out there, promote your application, get word of mouth and your user base going, and make a solid app, and you can be up there with any of these applications. When two apps have comparable features and prices, it all comes down to who is doing the work outside the App Store.