Caramall - see below. Try this if you haven't already. I have not had a problem regulating the temp since using this approach....
Repost: My heater was running hot too but I stumbled on to something that took care of the problem, and it is real simple. Instead of setting the Mode to where the heat is only coming from the lower vents or the upper and lower vents, set it to where it's coming out of the lower vents plus the defrost vents. When you set it to that mode, the A/C light will come on but you can just hit the A/C button to turn it off. I have not had a problem with getting cooked since I started doing this. Now, the 70 degree setting is quite comfy, where before if I had it at 66, it was very warm and I needed to crack at least one window or the sunroof.
Many people have also complained about running the defroster in the summer, since it wants to blow warm air and quickly heats up the interior when that is the last thing you want. If you use the same mode setting as above (lower vents plus defrost vents), but leave the A/C light on, you will find that it defrosts with much cooler air.