I haven't had any overheating problems with the 3G-S, and I've used it quite a bit in the Texas heat. And it's been a scorcher lately.
With that said, I'm not sure how I've ever lived without an IPhone. It's worth every penny, and then some. I purchased from the Apple Store in the local mall, and I was in and out in less than ten minutes, and it was ready to go right out of the box.
Here's my initial thoughts after a few days of use:
I'm having lots of fun with the restaurant locator apps "Yelp" and "UrbanSpoon". Both are free, and worth a try.
Also, I've ordered a case and screen protector: The Switcheasy Capsule Rebel Serpent. It's a silicon shell with a hard plastic "spine" on the back. Looks pretty cool, too. It includes a transparent screen protector as well. I'll post some impressions of it when it comes in. In the meantime, I've been using the Incipio Orion Sleeve. It's your basic soft leather sleeve, but it has a handy pull tab that pops the phone out of the sleeve for quick access. Highly recommended.