I just got through re-watching the "Red John" episode and would like to make some comments:

1.  The episode itself is very well done.  I know everyone wants answers to "who, what, when, why, and how" but Patrick doesn't and says so.  All the fluff that people on this and other websites are arguing about DOESN'T MATTER.  All the trivia is not as important as we think.  What is important is that Patrick found/killed Red John and got his revenge. 

2.  No one was going to be completely satisfied with the final suspect.  I understand those who wanted it to be Stiles, Partridge, Hafner, etc.  But someone had to be Red John.  It was NEVER going to satisfy everyone.

3.  I thought the final scenes were well done.  Patrick had a chance to NOT kill Red John but had to to be true to his mission in life.  It could not have happened any other way.

4.  The final scene with Patrick running was especially moving.  He is running away from his past (mother and young daughter holding hands), his present (watching his daughter slide down the slide), and his future (old man/woman holding hands). 

I, as may of you, did not envision this as Red John's end.  However, if you watch the episode objectively, the ending is true and terrific.  Everyone thought that the CBI and the FBI were enemies.  The subsequent episodes have shown this not to be the case. 

I, for one, do not hope the series gets cancelled.  I became a Mentalist fan about two years ago and have followed it religiously ever since.  It is a good, entertaining show and I hope it goes on.