I just twittered this, but figured I'd share it here as well. Adobe has released a ColdFusion 9 Performance Brief. You can download the PDF here:
If all you care about is overall server performance, then the numbers are impressive. ColdFusion 9 comes in at 40% faster than ColdFusion 8. Compared to ColdFusion 7 (sorry, "MX" 7), ColdFusion 9 is six times faster.
I'd suggest digging into the brief though as it goes into details about what features were worked on. CFC object creation is a big one - clocking in at 8 times after than ColdFusion 8. I've already talked about the createUUID() improvements, which probably don't matter quite so much, but it's cool to see a 10,000% improvement there anyway. I really like the 800% Flash Remoting improvement. Flash Remoting is already a great way to seed data to your RIA and that type of improvement just makes it even better.
You should also make note of the new caching features. The brief calls them out separately. For example, using "Cache Template in Request" can improve performance by 50X. I need to dig into that a bit more but it seems like that plus "Trusted Cache" could be pure gold for a production server.