I've had the HTC Droid Eris for a few days and I've been very impressed by this thin, small device. It's a great smartphone for those who wish to have a light, touch-screen device. Android is a great operating system and I like how you can easily find and install apps through the "Market." This "App Store" feature is also found on the Apple iPhone and the BlackBerry Storm/Storm2. You can easily find and install apps directly from your smartphone. There's no need to sync your phone to your PC first.
Windows Mobile has evolved from an era when we used to download installer files to our desktops/laptops in order to install apps. I predict that Windows Mobile 7 will change all that through the development of some type of universal "app store." If this doesn't happen, then Microsoft will continue to lose its grip on the smartphone market.
If you're familiar with the iPhone interface, then you'll quickly learn how to navigate an Android device. If you've grown up on Windows Mobile or PalmOS, then you'll still learn quickly, but you'll find some refreshing changes that simplify the smartphone experience. As I play with this HTC Droid Eris, I'm more convinced that Android will quickly dominate the smartphone market and that even more consumers will switch from standard mobile phones to smartphones.