I received my S3 via UPS this morning and I have to say, this might be the best phone/device I've ever bought. I could list some things I love about it but it's probably along the lines to what's been posted in this thread already by other users. I do not, however, like how quickly it heats up at the bottom, makes it uncomfortable to hold after a bit, but with a giant high tech screen I guess that's part of life. Otherwise, this thing is incredible. Very solid all around.
If you have a bunch of processes running in the background it will heat up at the bottom. Means you are pushing the cpu hard. It will get up to around 118 degrees and not much more. If it reaches much higherthan 125, i'd say there is a problem with the phone. There are a few apps out there with alarms that can warn you if the battery gets to hot, cpu gets to hot, battery getsbelow 5 percent, etc...
For thecar, I have always used an ac vent dock. This way when the ac isblowing it keeps you phone nice and cool. Been doing this since my first iphone. A cool phone is a happy phone.