Apple's iPad App Store has been updated and added a new search filter feature. The search filter feature allows you to filter application searches by category, release date, customer ratings, price, and by device's that support each respective application.
This is a very useful feature that will undoubtedly make finding apps a lot easier, and less convoluted. However, due to the amount of screen real estate this feature needs on the iPad, it's unclear if it will ever make it to the App Store on the iPhone and iPod touch.
Hopefully Apple can redesign it in a way that optimizes it for the smaller screen size, because it would be a pity if iPhone and iPod touch owners were to be left without this enhancement.
For now, search filters are only to be found on the iPad's App Store though -- they haven't even made it to iTunes.