Personally it is not a great film but it is not a bad film either I give it a 6 and half out of 10 Jackie Gleason was gold in the one playing both roles Justice and The Bandit although Jerry Reed looked and acted like a jackass in this one.
Personally I found the second film hard to watch because it basically aired all of Reynolds and Fields dirty laundry for the world to see something I watch films to aviod and that is reallife.
I totally agree with you that Part 3 was more watchable and fun to watch than Part 2 due to Jackie Gleason's performances as both Justice and the Bandit and I thought that Mike Henry was at his best in Part 3 and it was great having them get more screen time, what I could've done without on Part 3 was the Enoses having a bigger role in Part 3, they appeared to have more screen time than the first two films combined and they were really annoying.
What I didn't like about the second one was the Bandit acting like a total embittered egomaniac who thought too much for himself and nobody else and the problems he was having with Sally Field was unbearable to watch, while Part 3 was more stupid than Part 2 at least that Part 3 was more likeable and laid back.