March 6 2008, Apple covered their roadmap for the iPhone SDK: http://www.apple.com/quicktime/qtv/iphoneroadmap/
That was JUST 20 months ago. Unbelievable.
Since then we've all gotten caught up in the AppStore hysteria, overnight millionaires (maybe), 100,000 apps and average Joes (or Janes) developing apps for the iPhone. This is a positively enormous change for mobile application developers, traditional Mac developers and mobile entrepreneurs.
Xcode and the iPhone SDK make all this possible. It's not just a toolkit to allow you to build apps for the iPhone, but an incredibly well crafted suite (lets not forget Instruments) that is designed to allow developers to do what they do best: develop something to meet their business problem.
Everything about Apples developer tools and Frameworks scream "focus on what you're trying to achieve with your software, we'll take care of all the mundane stuff". 1 button is all it takes to get your software compiled, installed on a device and running in debug. This doesn't come as a surprise to any of the 'old school' OS X developers, but sometimes we need to be reminded about how awesome this toolkit is and how much we take it for granted.
The economist in me continually nags that any time I waste messing around with development tools is time I'm not spending on making my software better. If Xcode and the iPhone SDK were pigs to work with, then we'd still have software, there just wouldn't be as much and it wouldn't be as good.
You could even go so far as to suggest that the iPhone SDK has created a significant competitive advantage and barrier to entry in the now hotly contested market of third party application development for mobiles. The iPhone SDK has a long and rich heritage rooted deeply in the NeXT era, it's not something you can just knock out in a few months.
Sure, there will be SDK's for those other devices, but will they be as good? I guess time will tell, but I wouldn't bet on it.
