Used to live in AK. Never had to use the stuff despite one close encounter.
But, I did 'play' with it one time against racoons....it was a dangerous situation...
moral of the story is that whatever i had was useful to about 15 feet - with the wind at your back. and if the wind wasn't at your back - it got you as much a the bear.
whether or not that's useful is for the bears to decide.
unless the technology has changed a lot in the last few years - and maybe it has - it's worthwhile up to about 5-10 yards if you know what you're doing and are patient and calm and don't mind cleaning the shit outta your pants.
Two buddies are hiking in the woods when suddenly they come across a bear. One guy drops his backpack and takes out a pair of running shoes. His friend says to him "What are you doing? That's not going to help you out run the bear!" To which he replies "I don't have to out run the bear; I only have to out run you."
I carry UDAP also. I have heard very positive reviews and have started venturing deeper into the woods with my own cubs. I have much experience at close range with spray designed for humans. I like the non lethal results.
I was way out in the wilds if SW Alaska last year with an outfitter who has over 30 years experience guiding. He carried a 12 gauge and each client had bear spray and a small boat horn (the aerosol kind). That horn was unbelievably loud and the two times he used it the bears couldn't get away fast enough. It was smaller than the bear spray we each carried.