Why Startups Could Use .NET, But Don’t 15 years ago
To your last point, with the nuget package manager it's becoming easier to integrate the latest and greatest into your projects. For example, here's a nuget package that makes sass and coffescript a 'one click install' in your asp.net project: http://blog.paulbetts.org/index.php/2011/05/16/announcing-sa...
But like you mentioned, being easy to integrate isn't enough, you'd still have to justify it, which in a big company is more difficult than a start up.