I don't know why people are disappointed if Red John is Bertram, I think it's genius. Yes he has been under Jane's Nose but we haven't really seen that much interaction with him. Apart from his physical appearance ( yes would have been better if he was younger like RAY), he has been the perfect Red John. He hasn't shown any weakness apart from being a bad poker player WHICH by the way, he probably faked to get a little closer to Jane...remember he dropped that important phone call that he didn't have time for ...FOR Jane. His eyes are dark, something really creepy about him.

His grand entrance, not afraid to be in the limelight. He said he heard GREAT THINGS ABOUT JANE. Jane asked him why he was there when they first met. He got a weird vibe, knew there was something up with him. He has been shown to favor Jane over lisbon at times. He hired him back when she was still dismissed. He probably didn't kill lisbon because he likes the set up between them. Lisbon keeps him in his job close to Bertram. Killing Lisbon and putting him off the rails at this time would be disruptive.

the meeting between the TT members. Well it is obvious NOW when he said " we should discuss this in private" he probably thought that Jane figured it out. HE was the one in charge.
he was the first on the scene in 6x01 with lisbon. he would have got/given the tipoff and have gotten the call for backup. He was in a good position of power.

He is tall and he stutters sometimes. Yes he is bald but everything else adds up. 
He never denied being Red John unlike the sheriff. Did I see Stiles looking at him briefly when he said " what one of us in this room"? I think I did.

Most of all it's genius because he is a man in power and red John would have to be in power to be able to recruit so many and to be always a step ahead.

lastly someone mentioned that redjohn would be foolish to wear a ring and get recognized...well I say that that scene with him sipping tea that was for us to see not anyone in the mentalist, therefore he does wear a ring.

Bertram is as good as any to be red john and the more I watch his scene the creepier he gets.
Yes I think maybe Ray would have been better physically but maybe I am being shallow lol just thank bloody god that it is isn't REEDE SMITH. I don't think I could stomach that.

I can't figure out Brett Though why kill Brett? Did Brett find something..DNA. What do the pigeons mean or do they mean anything. Anyway, it's pretty definite that it's Bertram.  There is one episode left there is no time to bring anyone back from the dead. I can't wait to see the reveal now.