I'm curious about how .NET will affect Python and Ruby applications. 
Will applications written in IronPython/IronRuby be so specific to the .NET environment, that they will essentially become platform specific? 
If they don't use any of the .NET features, then what is the advantage of IronPython/IronRuby over their non .NET counterparts?
If you create a library or framework, people can use it on .NET with their .NET code. That's pretty cool for them, and for you!
When developing an application, if you use .NET's facilities with abandon then you lose "cross-platformity", which is not always an issue.
If you wrap these uses with an internal API, you can replace the .NET implementations later with pure-Python, wrapped C (for CPython), or Java (for Jython) later.
How will Python and Ruby applications be affected by .NET?