Apple has requested that developers who want their apps featured in the grand opening of the iPad Apps Store get their coding completed by March 27. Apple says quite clearly, "[o]nly apps submitted for the initial review will be considered for the grand opening of the iPad App Store."
Those who submit after that date can't be guaranteed placement in the iPad Apps Store at launch. Come to think of it, even those who do submit by 5PM, Saturday, March 27 can't be guaranteed placement in the store. Apple only says that it will acknowledge receipt of submitted apps, and provide feedback on the submitted apps' "readiness for the grand opening".
Apple will only accept applications that have been developed using the latest beta of the iPhone OS 3.2 SDK, which was released just the other day.
If you're a developer willing to brace the iPad Apps Store approval process, get your developing on. You have eight days left to create a killer app.