We bought a new HHR LS on 2007. Somewhere around 36,000 miles started to hear rattling sound front end. Got worse and took car to GM authorized service. Similar to another posting I saw on this blog, both struts were bad as well as steering column shaft and sway bars. GM and service were good and everything was covered under warranty. Understood from service rep that this might be a common problem with the HHR. Sounds like poor manufacturing. So if you have a '07 or '08 be aware you may be encountering some issues in these areas.
Gas mileage, looks, and lots of storage space.
Window buttons on drivers side door. Mudflaps to avoid paint chipping. Arm rest on drivers side seems a little high.