Frederick, in this forum post you mentioned that you would have CDN support for things like user uploaded avatars in Buddypress, for example.
In my site, users have either Gravatars or user uploaded Avatars, but when I turn on CDN it breaks the functionality. Here is how it breaks it, the user uploads an image and then they are then unable to crop the image because now the site is looking for the image to be at my CDN location, whereas it is at on the local machine initially.
Is this feature available yet? Perhaps in a developmental version? (I'm running 0.9.1.1 on a 3.0.1 WordPress with Buddypress as well.)
If you haven't implemented it, perhaps you can do something similar to what this guy did with WordPress Amazon S3 Plugin where he moves the files to the CDN after a certain amount of time?