A centralized repository for Blackberry applications is a good idea. There are a plethora of applications and themes for Blackberries, but they are scattered about the Web on, sometimes confusing, websites. The problem is compounded when the software is installed via the Blackberry Desktop Software rather then being downloaded directly onto the phone. Sometimes, it's just nice to download software to play with. If the easy to navigate and the software is easy to install while using the phone, the store will be a big step up.
While the store is a good idea, it's not above criticism. Some people are criticizing the $2.99 minimum price as being too high, citing the $0.99 minimum at the iPhone store. Along with the $2.99 minimum, RIM is charging a $200 administration fee for every 10 application submissions. While people aren't happy about the decision, it could work to keep the clutter down, and it has been suggested that Apple should implement a similar policy to cut down on the chaff in the App Store.
Platform fragmentation is another concern. App World will only stock software designed for Blackberries with OS 4.2 and a trackball, but the current Blackberry line is a hodge-podge of phones with varying equipment levels. The Bold has WiFi, GPS, 3G radio, and QWERTY keyboard. The Storm has GPS, 3G radio, and a touchscreen, and the Curve and Pearl are older pre-3G models with their own hardware specs. Developers are worried about having to support all of the devices or being locked to one device.
Once RIM opens Blackberry App World, only Nokia's, Microsoft's, and Palm's store will be left waiting in the wings.