General Leupold opinion- They make absolutely wonderful, durable, clear glass at, normally, an affordable comparitive price. I have a could LR/T Mark 4 scopes, and wouldn't trade them for anything.
Mark 6 opinion- I have never used it personally. I am a leupold fanatic, but even this optic is out of my price range. If you can afford the $1900 or whatever outrageous amount they are asking, then I am sure that you won't be disappointed with it. However, it is just too expensive for what you get...in my opinion at least.
The 3/4 MOA adjustments at 100 makes for very accurate shooting adjustments on the dials. That is, as long as the ammo, gun, and shooter are up to par. As far as the TMR reticle. That is the reticle I use in my Mark 4's. It makes ranging the target on an unknown distance qual a piece of cake! Much more accurate than the mil-dot in that aspect. But in 3-gun, you are probably not going to need the TMR's capabilities. And I don't know much about the CMR reticle, but it looks like there is A LOT going on. Anyways, if you make the purchase, let me know how you like it!
-Paden