It was a life saver on my trip two weeks ago. We were on a 2 week 4k mile trip through Australia. On day 3 we got a flat in the rear tire, in the middle of the outback. No possible place to have it changed. So a few plugs and a can of tire slime and we were on our way. Our friends were amazed when we pumped it up and then just drove down the road for hours on end, never stopping to check the tire pressure... when we pulled into a rest area to take a break, they all were like "wow, you have a lot of faith in that plug..." my answer - "Nah, not really, but I do have a digital read out of the tire pressure on the dash and it will tell me as soon as it loses a pound!"
Without a doubt that was a trip saver. With it, we were able to 'safely' complete our trip knowing the tire was not losing air. Without it, we would have been doing a nervous nelly stop every 30 mins while I checked air to see if the plug was holding or not... That would have definetely caused us to have to detour and cancel our trip midway through it.