Does it mean that you can now develop generic applications that use the industry standard widely supported API and deploy them with IIS?
Several things you should know about IIS and FastCGI:
It does not support multi-threaded FastCGI applications. That means your generic application would be able to process only a single request per process.
Even the standard example that comes with the most popular fastcgi library implementation would not work.
This basically means: you can't implement with IIS/FastCGI long polling techniques, or share some cache between multiple worker threads of the same process.
It does not allow you to use external FastCGI applications - something very common in web servers world. All popular web servers: Apache, Lighttpd, Nginx fully support it/
IIS must manage your application life cycle and does not allow you "to do what you think is good for you".
This basically means only one things: FastCGI support for IIS was designed to run PHP... Nothing more.
One again - Microsoft takes very good generic standard and... succeeds to implement it in the most horrible way.