I've had my HHR for about a month. I bought the 2LT model with the 2.4L engine. All I can say is the car is loads of fun to drive. I keep finding excuses to just get in the car and go somewhere. Performance-wise, the 2.4L engine is decent if a bit slow on initial acceleration. Handling is actually pretty good with the improved suspension that comes with the 2LT package. Brakes are a bit weak though. Interior room is great. I traded in an '03 Sonata and the HHR has a lot more room in the driver's seat and is much more comfortable to drive. Visibility can be a bit of an issue until you get used to its blind spots.
Styling: I like the retro look. Loads of cargo space for a small car. Overall fun to drive. Good gas mileage - I get about 24mpg in city driving.