Spark, the question is not whether you were experiencing discomfort, it's whether your ability to shoot or stab was impaired.
Or in other words ... rather than ask yourself, "Do I want to go through that again?" Ask yourself, "If that had been a real fight what would I have done to the other guy after he sprayed me?"
If the answer is, "Nothing," then your experience is evidence for the efficiacy of pepper spray. If the answer is, "I would have gone on shooting or stabbing or choking him or whatever I was doing to him before he sprayed me" -- possibly with less effectiveness due to impaired vision and breathing, possibly with increased enthusiasm....
From what you've said so far, it isn't clear which side of the question your experience weighs in on....
Pepper spray does have some effect on most attackers (unlike "stun guns"). There are numerous reports of it being used in successful encounters, usually in combination with other weapons and techniques but sometimes pepper spray alone has been sufficient. It is disturbing, though, that many people seem to think pepper spray is the universal answer to all close quarters attacks; that it will stop any attacker and there's no need to practice any martial art but the use of pepper spray or carry any other weapon. It just ain't so.
-Cougar Allen :{)