The power of the Internet is in the server, not in the browser. I agree wholeheartedly that tools and applications are important, but platforms are high on the interest list too. Consider the embedded Linux vs Palm war that's brewing. From a hardware vendors point of view they have a choice - Linux is free, but doesn't have the current application support that Palm has. Just one example off the top of my head about why looking at platforms is important.
Applications are clearly a derivative of the platform and the support around that platform.
One of the reasons Microsoft have succeeded is they were able to seed and grow a developer base that is now second to none. So in effect a unified platform fosters great applications.