I've been tinkering with App World since the launch 12:01 AM, and I'm quite impressed. It's clean, organized, and easy to use.
This is the main page that you will see when App World starts up (once you accept the Terms & Conditions). As its name suggests, the 'Featured Items' section offers those applications that are found to be useful to BlackBerry users. Below the featured programs, you'll see four buttons - from left to right: 'Categories,' 'Top Downloads,' 'Search,' and 'My World.'
As you would imagine, the 'Categories' section breaks the applications down by type, making it much easier to find the programs that interest you the most. Fairly self-explanatory here.
The 'Top Downloads' section lists the 25 programs that are most popular at the time. Though I've only used the store for one day, I have found that most of the applications in the list are (not surprisingly) free.
Again, self-explanatory. The 'Search' tab allows you to type in what you're looking for, and delivers a list based on what it thinks to be the most relevant results.
'My World' lists the applications that you have downloaded from the store.
All things considered, App World represents a great start for Research In Motion, but they certainly have a long way to go if they want to be a serious contender in the application store market. As much as I hate to reference Apple at every turn, the company has 24,000 more applications in its App Store. Furthermore, RIM is only accepting payment via Paypal at the moment, and though it has promised additional methods of payment soon, it needs to move quickly to make the experience as smooth as possible. I can't wait to see the impact of the store once these small hindrances are ironed out.