Check the archives of Ruby-Talk.
The guy in charge of IronRuby is a nice guy who originally started  
doing it on his own. He seems to be quite sincere about making  
something right. I wouldn't want to be him for the number of times he  
has to pre-defend IronRuby before it's even finished, but he must  
have expected some paranoia... it is MS, and they've got a reputation.
It's coming. That's for sure. So let's just wait and see.
Let's hope for the best. Do anticipate Windows-specific API calls to  
be made available. Anticipate explaining to newbies who start with  
IronRuby, that those Windows-specific API calls won't work on other  
platforms.

I would be curious to see what would happen if they tried to create  
IronRails.... DHH would not be pleased I suspect...