In the e-mail sent to developers, Apple tells them to download the 8th version of the SDK, which was recently made available. This new version provides developers with the tools they need to finalize their applications and test them. It also directs them to a special portal that provides detailed instructions on how the submission process works, how to maximize exposure, and other vitals. Unfortunately, nondevelopers aren't yet party to see how this all works. Someone is bound to spill the beans at some point, I am sure.
Since no one knows how many developers will actually be submitting applications to the Apps Store, it will be impossible to determine the percent that Apple will have a chance to approve before the store opens. It would be great to have some information on how the approval process takes place, who does the approving, how long does the process take, etc.
We have to assume that developers who are serious already have finalized their applications to the fullest extent possible. Given the demonstrations that we saw at WWDC a few weeks ago, we know what at least 10 companies have been up to since the SDK was first announced back in March.
In two weeks, we'll find out how many others have been toiling away on fun and useful applications for the iPhone.