Sprint and HTC this morning released the expected software update for the Evo 4G. Said to be improved in Version 1.47.651.1 are Wifi signal strength reporting, improvements to the Exchange ActiveSync security policies, and network improvements to address battery life.
The update takes just a few minutes to download and install. You can get it by going to Settings>System update>HTC Update. Sound off in the forums if you're seeing improvements.