Yes to test on multiple different devices.
Up until recently, this was the only way to test Sense UI (HTC's overlay - they recently released a developer kit, I haven't played with it). It is much easier to have MotoBlur, Sense, and TouchWiz devices around, instead of dealing with custom configurations and multiple development kits.
It is a lot easier to play with a mobile app on a device, to really understand how it works. While you can pretty much configure the emulator to simulate most things, it is usually a lot easier to test on actual devices (not to mention faster).
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Mike Wolfson Phoenix, AZ, USA
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