Planning to do coolant flush soon. Should be the first time for this car. There is some recommendation on the HHR boards to go ahead replace the thermostat while the flush is done. It would be an excuse to try a warmer thermostat, but I don't see the point if the old one isn't broke and has plenty of life left.
I would have had to pay over $80 for the proper 192 F thermostat at the Honda dealer up here in Canada.. they gave it to me because they had to order it in and it was late getting in.
I'm sure the girl that gave it to me was in trouble after that, but hey ..customer service was nice from a dealer for a change.
I'd say if 180 is what the manufacturer recommends, that's what I'd put back in. If you raise it to a 195 the computer may start richening up the mix or playing with the timing to try and cool it back down.