You can ask the dealership to show you the original MCO (this is turned over to the RMV when the car is first titled).
If that's not an option or if you have your suspicions (as you should), you can check with your insurance company and have them run a title check on the VIN. Some will do this for you, others won't. If they don't, you can run a Car Fax report (or ask someone who has a subscription to run one for you) which will show if/when the vehicle has been titled.
The second thing you want to do is check the status of the warranty. A warranty usually starts when the car goes into service as a demo, even if the car hasn't been titled, so you'll probably lose a few months & miles on the warranty. You can contact one of the Chevrolet Customer Care reps who have an account here (Katie has assisted me in the past) and they can confirm the dates.
When I was shopping for my Volt I ran into a few dealerships who insisted the Volts they were selling were untitled and/or had 100% factory warranty, when that was not the case. In some instances it was an honest mistake, in others they were trying to screw me.
The title is a deal breaker (worth $10k in MA) but the warranty wouldn't bother me if the price was right. You may be able to get the dealership to give you a free or discounted extended service contract to make up for an warranty that's been activated, or discount the car enough that it's worthwhile.