It won't be easy: BlackBerry's App World, Palm's App Catalog, Microsoft's Windows Mobile Catalog and Google's Android Market have only a fraction of Apple's offerings.

CNN: New iPhone 3GS heats up smartphone wars

Running Windows is all well and good, but when you're running the RT flavor, which strips compatibility with the entire, massive and still-swelling catalog of Windows applications, you're left with a desktop-class operating system completely bereft of any desktop apps.

ENGADGET

While Windows Phone has been gradually building its catalog in the years since it launched, BlackBerry's debut lineup was surprisingly strong.

ENGADGET: Switched On: Battling for the bronze

That's why Windows 8 opens in the start screen, why Microsoft is working to build up a large catalog of tablet-type apps that run only in the start screen, and why the traditional desktop has been relegated to a mode you reach by clicking on an icon on the start screen.

WSJ: Mossberg's Mailbox: A New View on Windows

Amazon scans customers' iTunes and Windows Media Player libraries and matches the songs on their computers to Amazon's 20 million song catalog.

ENGADGET: Amazon updates Cloud Player with 256 Kbps matched files, faster import, direct delivery (update: Roku, Sonos coming soon)

Seamless Shopping and Reading: Elevating the shopping experience to new digital heights, NOOK for Windows 8 customers can browse over 3 million books, magazines, and newspapers through NOOK's expansive digital content catalog, learn more about the book (including details and reviews) right from within the app, and tap to purchase and begin reading in seconds.

ENGADGET: Nook app comes to Windows 8 with clean Paper-like design

Through the power of the cloud, it effortlessly integrates the music experience across your tablet, PC, phone and TV.1 With more than 30 million songs in the global catalog, Xbox Music begins rolling out around the world tomorrow on Xbox 360 and later this month on Windows 8 PCs and tablets and on mobile phones, starting with Windows Phone 8 at launch and additional platforms later.

ENGADGET: Xbox Music heads to Xbox 360 first tomorrow, PC / tablets on Oct. 26, WP8 soon after; we go hands-on