I was told by a guy that he used it when he got a flat and it did not
pump up his tire completely, but got enough pressure to get to a gas
station with air. However, he said that was 6 weeks ago, and the tire
never leaked again.

While I do think the stuff will pump up a tire with a small leak, I
tend to question the permanence of the repair. I know I would have
had the tire in the shop the next day. I just can not see how this
stuff can make a permanent patch on any tire.

What is your opinion and experience?

My opinion is to always carry a spare tire and use that when you have a
flat.