Android's Home screen is simple and stripped down -- all the app icons can be moved or deleted, except for three unmovable icons: the Dialer (for making a phone call), the Application Tray (an overlay that shows you all your apps) and the Web app.
Apple's iOS interface is the iconic design that people have come to associate with smartphones: a spare screen with app icons arrayed in a clean grid.
Windows Phone 7 is organized around a series of hubs -- displayed as tiles -- that deliver information to you or let you perform certain tasks.
There are a variety of ways to find and download Android apps. The primary one is the searchable, browsable Android Market, available both on Android devices and the Web.
There's a single place to download and install apps for iOS -- the Apple App Store, which makes it simple to browse and search for downloads, and easy to install them.
When it comes to openness, Windows Phone 7 is closer to Apple than it is to Android, because you can download and install apps only from its own store.
Android automatically integrates and syncs with various Google services, notably Gmail, your Google contacts and Google Calendar.
Like Android, iOS has a unified e-mail in-box for checking multiple mail accounts. However, iOS can sync contacts and calendar information with Outlook 2003 and later versions.
Windows Phone 7 has clearly been designed to be the centerpiece of a Microsoft-centric world. The version of Outlook built into the operating system works and syncs as you would expect -- seamlessly.
Choice and customization is baked into the guts of Android phones, not just into the main interface. Press the Menu button when you're in any app, and you'll invariably get a host of settings.
The iOS Settings app gives you control over all basic features, including sounds, brightness level, Wi-Fi use, how notifications are handled and more.
Microsoft has built and marketed its mobile operating system for people who want to get their work done quickly and efficiently, and don't want to fuss with customization and settings.