I haven't had a chance to mount the Mark 4 yet, but have been playing around with it a bit side-by-side with my Vortex scopes. The glass does look to be a slight bit better on the Leupold, but really hard to tell...I need to get the scope actually on the range and see how it stacks up. I'm still not impressed with the turrets, entirely too mushy. They are no where near as tactile or crisp as the Vortex, and feedback isn't as good. I can rotate the turrets on any of my PST's in the dark in a snow storm, and know exactly when it "clicks"...not so much with the Leupold.
Plus, I have now invested in too many different types of reticles. While I don't mind the TMR, I would prefer an EBR style reticle simply because that's what I have in my PST's. Of course, I knew this going in with the Leupold, so that is my fault. I may look at swapping for a PST with EBR-MOA, as that's what I have in my Vortex (as well as my US Optics, keeps all the math the same).
Don't get me wrong, I think the Leupold is a solid optic. I just expected a little more out of a scope that is close to $1k.