I actually really enjoyed the lunch interview for Amazon in Seattle. The 2 interviews before and the 3 interviews after were strictly technical, and although each technical interviewer offered to answer any questions I had, it was clear that the time was up and I was scheduled to be moving on. The lunch interview was a good opportunity to find out more about the hiring team and the company, and was the only conversation I had that didn't start with "please write code to solve this problem" or "how would you design this". Although you're right, trying to eat while answering questions about yourself was challenging, but since I knew that going in, I didn't order very much food. But the cafeteria was pretty awesome!

And I'm surprised at the poster's experience, I received a polite rejection email just a few days later. I hate when companies just cease communication after an interview...at least let me know, regardless of the outcome; I'd rather receive a rejection notice than wait and wait. But I guess it's a big company, experiences probably vary rather wildly.