Beyond the classic apps
Basic data-driven apps are just the first thing you'll see. Microsoft recognized that many smartphones are often more camera than phone today. I'm sure many people use Instagram or the photo-sharing features of Facebook more often than they talk and listen to the voices of their friends who actually ring them on the so-called phone. If you want to develop software that uses the camera on Windows Phone 8 devices, a big corner of the SDK is waiting for you.
Microsoft calls one class of apps a "lens." If you happen to write a lens, it becomes available in the built-in camera application. The user will pop up the camera and swap "lenses." A lens app is more a plug-in for the built-in camera than a stand-alone item.
I think this is a good feature for the user because it cuts down on the clutter. It also simplifies some of the work for the developer, but developers may feel like they're losing their identity in a demotion from full-fledged app to mere lens. The lens creator now has some user interface guidelines to follow. While this may lead to ego deflation, it makes the camera experience simpler and more consistent for the user.
The Windows Phone 8 emulator, which lets you test for devices at three screen sizes, offers a nice way to test the reaction to acceleration. Note, however, that it runs only on Windows 8 and modern hardware.
Some of the lenses will be devoted to nostalgic fiddling with the colors or changing the contrast until it looks like a picture from a disposable plastic camera made in 1974. But a Lens app can be much more than a color filter for postprocessing. You can add controls that will do anything you want to do with the image, including posting it to a website.
The camera is not the only part given special treatment. You can now write "VoIP apps" that integrate directly with the phone. Although Microsoft paid plenty of money for Skype, the company is ready to give any VoIP app first-class standing in the API. I'm not sure how this might upset the people who own the cell towers and pay for them by selling minutes. However, it's a forward-looking solution that recognizes there's more than one way for a mobile phone user to place that one telephone call they make each year on Mother's Day.
The tower owners might also take note of the Data Sense feature, a meter that tries to track how many bytes are going in and out of your phone. The good app developer can use the Data Sense API to check on usage and, perhaps, delay downloading that file until the user is connected via Wi-Fi. If the app developers pay attention -- and they should -- users will like the control this gives them over their monthly ration of cell bits.
App Store in Windows clothing
It's not all good news. Microsoft is following Apple down the road to programmer serfdom by adopting strict central control of the Windows Store app store, and early stories are mixed. Some developers are reporting the same kind of frustration that greeted developers at Apple's App Store. The economic model of apps sold at $1 or $2 can't support the lengthy code review that programmers need, so the app store turns into a black box where a bunch of overtaxed reviewers reject items with inscrutable messages.
The economics will take some time to work out. Microsoft is offering a steep discount for developers who want to start submitting apps; it's just $8 to join. The game for the company is to attract as much talent as possible to build a viable app store, though the move seems also to have annoyed a fair number of Windows Phone developers who recently paid $99 for the same privilege.
Programmers with experience developing for Microsoft's platforms should be overjoyed by this SDK, especially those who are well-versed in XAML, C#, Visual Basic, or C++. Finally there's a good path to using that knowledge to create an app running on a thin tablet or a mobile phone.
The SDK, though, is more than just an opportunity to catch up with the iPhone or the Android world. Some parts of it offer new features such as lenses and VoIP apps that will create a unified world that's simpler and more harmonious for the user. This alone promises that Windows Phone phones will have some advantages - if Microsoft can attract enough programmers and phone owners to nurture an ecosystem.