I fished the Kingston open as an AM the first two years. (2010 and 2011)
For the most part, it was a pretty positive experience. I got to fish with 6 different "pro's" during those 2 events, and in all honesty, it was a pleasure fishing with 5 out of those 6 anglers. Each had a different approach to the water we were fishing, and i learned quite a bit from all of them.
However, 1 of the anglers i was paired with, (i actually didn't even draw this person originally. The morning of the second day, i found out that some pairings needed to be switched around. So there i was, waiting at the ramp, and i thought i was going out with a really great angler...instead, after the switch, i ended up going out with a "pro" who's main boat had issues day 1. He wanted to pull out of the event, but was asked not to...the boat we ended up fishing out of was a 17' aluminum. so needless to say, we weren't going very far from the the blast off site that day. All 5 of the fish we weighed in, I caught. The guy i was fishing with, did not want to be there and he made no attempt at hiding that fact.
This was one bad experience out of 6 days of fishing.

Some great experiences were had too. A great example was my day 1 partner during the second year i fished it. Andrew Shufelt. The day was canceled due to high winds. I had never met him before that morning, and instead of saying goodbye and going on his way, he asked me if i still wanted to go out fishing. We drove an hour north and spent the day fishing Big Rideau. It was an awesome day, and something that went far beyond anything i expected.

I definitely don't have any regrets fishing those events. They were a great introductory to some of the larger scale events in Ontario, and it was a lot of fun fishing Big water. Something i had never done before.
The downside to it was the cost. They weren't cheap.
Now i knew what i was getting into when i signed up for them, and was fully prepared for it...but for someone sitting on the fence who might not know what to expect, it can add up quick. Between the cost of motels, food, gas, the entry fee itself and time off work, it was a pretty expensive 3 days of fishing.