Since this scope is going to accompany me on a pronghorn hunt next weekend, I have been spending a LOT of time with it.
I will put a together a final review video after the hunt, butfigured it was worthwhile to offer some thoughts prior to that.
After the hunt, I might be somewhat swayed by whether I am successful or not.
For the time being, I am my usual self, relatively unaffected by buck fever.

I currently have two Mark 4HD scopes:
2.5-10x42 FFP with illuminated TMR https://alnk.to/gVLq1hd
4.5-18x52 FFP with illuminated PR1-mil https://alnk.to/eZH5eia

I have spent a good amount of time with both, but more with the 4.5-18x52, so I will focus on that one.

In a nutshell, I rather like this scope. It has stayed zeroed on a couple of guns, primarily Stag Pursuit in 6.5PRC. Tracking looks to be consistent. I did quite a lot of turret spinning.
Optical quality is quite good. There is some CA on very high contrast targets, but it is mild. Overall, the image is very pleasing. FOV is mid-pack with around 20 degree Apparent FOV (see attached tables). Note that FOV numbers published on Leupold website are lower than reality. The numbers in my table are what I measured.
Eyebox is nicely forgiving. This is a comparatively common compromise for Leupold designs. They throttle the FOV a little to get a nicely flat image with a very forgiving eyebox.
It is not a particularly compact scope, but weight is not bad at about 27 ounces. If you do not need to use it with a thermal clip-on, it is a very capable crossover scope that can go hunting with you or help you make weight limit for a competition. I did some basic arithmetic anc concluded that if I were to put it on my Fix, I would easily make it into the NRL Hunter Open Light class (under 12lbs) with a suppressor and bipod.
The rifle you see in the pictures is heavier than the Fix, so it weighs 13 pounds as configured with Q Jumbo Shrimp suppressor (https://alnk.to/g3bDbPE), Gunwerks Elevate 2.0 bipod (an exceptionally nice bipod that deserves its own article https://alnk.to/87Zx36E) and Mark 4HD 4.5-18x52 in Leupold's Mark 4 rings.
While we are at it, these rings are 1913 spec, not STANAG, so they do not make it onto my list of recommendations. The scope, barring some unexpected issues in the field, does so comfortably.
Reticle illumination is controlled via a push button. I am not a huge fan of push buttons, but they are compact and they mostly do work.
Illumination is done fairly nicely and there is an electronic level where the reticle starts blinking if the scope is tilted. I have not been using it all that much, but it is helpful at longer distances.
The reticle in the scope is illuminated PR1 Mil. It is a fairly basic Mil-hash design that looks like evolution of the TMR, to some degree. It is based around 0.2mrad hash mark spacing, which I am very used to. The lines are probably on the thick side by modern standards, but I think it is sized just right. The center dot is 0.05mrad. The main stadia lines are supposed to be 0.04mrad according to Leupold, but they look a little thicker to me. Either way, I found that the reticle was fairly easy for me to use across the whole mag range.
With this scope, I dial elevation and hold for wind.
The windage turret is covered. The elevation turret is Leupold's M5C3 with zero stop and zero lock. It is similar to the one in the Mark5HD, except they kept it at 10mrad per turn, instead of 10.5. I think I prefer 10.
There is a slight amount of slop in the clicks, but not enough to bother me. We'll see if it gets looser with use, but so far so good. Resetting the turret is pretty trivial: loosen two screws, slip the turret to where you need it, tighten the screws. It is not a highly original method, but it works.
In terms of size, this turret is just right. It is large enough to comfortably manipulate, but not very tall. In terms of the form factor, it is easily one of my favourite design on the market today. Click feel is decent, but not spectacular. It is no Tangent, but it does not have a Tangent price tag either. As a practical matter, I never skipped a click, but there were several times when I did not quite trust my count and had to look at the turret. I thought I skipped a click, but I hadn't.
As I spend more time with the turrets, I trust them a little more every time. Since I am preparing for a very specific situation (New Mexico pronghorn hunt), I am training primarily in the 300 to 400 yard range. I do not anticipate having to take a shot beyond 300, but it is good to hedge a little. I did not look at the reticle dimensions super accurately, but so far they seem to be true, but, again, I am checking it at 300 yards. When I am done with the hunt, I'll take it off the rifle and finish all my usual checks: tracking on the collimator, side-by-sides with other scopes, etc.
Interestingly, when I was putting the spec table together, I did a search for scopes in the $1000 to $2000 range that are equipped with a 50-ish mm objective diameter and top out between 16x and 22x.
At ~$1700 dollars, Leupold has nothing directly comparable. Razor HD-LHT is a couple of hundred dollars less. NX8 is $250 more. Everything else is even further out.
When you put it up against the competition, I think the whole Mark 4HD series is a stronger competitor than the Mark 5HD, partly because it is a nice scope and partly because it sits in a price range that is decidedly less crowded than Mark 5's.
Bushnell DMR3 lacks illumination and is heavy.
GPO 2.5-20x50 has a garbage reticle.
The more I look at the field, the more it appears that Leupold picked a very nice price niche for themselves and populated it with a well packaged, reasonably light and optically sounds products.