A deep usage tracking and reporting system. One of the most exciting (or potentially creepy) parts of this will be Google's approach to tracking how users are interacting with its OS. The company spends a considerable amount of time and resources on tracking user experience on its sites both with extended betas, and internal research studies. Having that same kind of tracking system baked into the OS can give Google a very simple way to see what's working and what's not.
As such, Google is likely to take a more extensive approach than Microsoft, which has a more limited system for tracking user activity on Windows. Users can opt in to a "customer experience improvement program" for Office, while Windows users have the option of sending information to Microsoft when applications or the entire operating system crashes. Google could go as far as keeping track of how long you keep your machine running at a time, or what times of day you use certain applications in order to create battery-saving hardware profiles.
More details about the Chrome OS, including privacy and licensing information are likely to be unveiled later this year when Google makes the code available as open source.