Those of you with EVO 4G's are quite fortunate to have the latest and greatest of the Android hardware, and once the guys at XDA get a version ready for release, you'll be even better off than the Nexus One owners running Android 2.2.
Here is the YouTube video of the FroYo build running on the EVO 4G.
In a related story, AndroidandMe is reporting that the HTC EVO 4G does indeed tether for free. It is also noted in the story that several apps are available in the Android Market which allow nearly every phone to do this. I wrote a story about the future of FroYo and the costs of tethering and we still have no definitive answers for all carriers.
According to the article, it seems that until carriers roll out some sort of software fix to their devices (or do what Sprint is doing, charging an extra rate for the EVO 4G, since it is running the stock Android 2.1 and can do Wi-fi tethering), you may be able to tether to a computer without any ill effects.
Here is the YouTube video from the article.
Image from Engadget