I had a service engine light come on and stay on as I was driving. Hit Onstar and was told that power steering issues, which caused me to call the dealer as soon as I got home. The dealer took me in immediately, while I waited for them to diagnose the car, I got 2 e-mails from Onstar which also warned me that the brakes and stability control systems needed immediate work!
The head of the dealer service department came out some time later and told me that the car just needed a "flash update". The other 2 problems were related to the first problem.
You can imagine how much I was originally freaking out! The first problem was troublesome, but all 3 at once!
Not to worry, GM has this sucker figured out.