The GPS function is the entire reason I am going to wait instead of getting a wifi only version. At home I obviously don't care about gps, but when traveling it will be amazing. And even when driving around if we want to find a place to eat or check out the location aware apps will make finding these places amazing. I don't actually think it will replace my cheap gps unit in my car for long trips or when I am alone in the car but whether my wife likes it or not she is going to realize how nice it is.
Now, if I had an iPhone I wouldn't be nearly as excited. But I don't and won't until it ends up on Verizon.
Even with my iPhone I'm still excited about the prospect of GPS Apps with iPad. In fact, my Local LTD app uses the GPS function and I'm currently working on upsizing/enhancing it for the ipad. I can't wait for this 3G model. It can't come soon enough.