Caught in surprise but it seems App Store app on iPad have added another column called as Purchased which is in between Categories and Updates section. In fact this option is available for Books and Music As well.
When you select this section you can see list of apps which you have bought from App Store. What is even more interesting is that you can also see list of apps which is not on the iPad.
So if you have a habit of maintaining a list of Apps which you have downloaded but deleted from iPad, you can throw it off. Using this option it is now very easy to re download the apps which you did bought but it is not there on your iDevice.
All the apps which are not on your iPad or iPhone can is marked with a cloud sign with download arrow in side it. I wonder if iCloud is behind it.
Interesting Spying Feature which is obvious :
In case somebody downloads an app on your computer or any other device using your account, you will get to see instantly under Purchased Section > Not on This iPad Section. I wish there was a notification system for this also :).
Though it will be easy to transfer from your computer, if you have backed up in your computer using transfer purchase option, but if you are not near your computer and want to show an app to your friend which you purchased but is not right there, is easy now. I hardly use it because it messes with my App arrangements on iPad
Summarizing Purchased section lets you see all the apps you have purchased from App Store. You can also sort between iPad or iPhone types of app. The best feature is you can also see list of apps which you have downloaded but its not installed on your iDevice.