We're still in the testing and investigation stage, but I think we'll be building a relationship with Railo in the near future.
You may want to change some of the default settings if you are running IIS and ColdFusion 10. There is a good chance that you will see significant stability and performance improvements.
If you are experiencing an incredibly slow ColdFusion 10 installation after upgrading, you might want to check IIS for script/handler mappings that still exist from the previous CF version.
I did a live presentation in which I upgraded a production ColdFusion 9 server to ColdFusion 10. Here are my notes if anyone is interested.