I come here seeking knowledge as well. The more I learn, the more proficient I can be if I can apply that knowledge in the field.
I worked in a few gun shops for a number of years off and on. Any time a new cartridge came out, some customers would line up waiting for their new "deerslayer." Others would denounce the new offering as either "too much for deer" or not any better than their "old '06." Some would take time and consider the application of the cartridge and use that for determining if it fit their needs. Many of the "deerslayers" would be on the used rack before the next season.
A cartridge in a class such as the 7mm Ultra Mag is not an average whitetail cartridge by any stretch of the imagination. Given the preferred habitat of the whitetail, and the most common method of hunting them, I would venture to guess that most shots are taken at close to medium range. I don't believe that the majority of hunters are shooting whitetail at distances approaching 400 yards. There are some hunters shooting whitetails beyond that range, but as the distance grows, the pool of shooters making, or even attempting to make those shots tends to shrink.
That being said, I have heard a lot of criticism for the ultra mag class cartridges due to extreme damage and the resulting loss of meat. When I hear comments like that, it makes me think that either the tool used for the job is not the correct one, or the operator doesn't know how to correctly apply it.
A comparison I like to make when talking about terminal ballistics (which can be understood by most individuals) is one that incorporates race cars and big rigs. Most folks who zoned out when I would try to explain ballistics to them would suddenly wake up and yell Petty, Earnhardt, or Gordon at this point.
Take a Formula 1 car zipping along at 200mph. Run it into the wall and see what happens. Due to the construction of the car, the velocity of impact, and the resistance of the wall, the car tends to fly apart, quite spectacularly, in many directions and in small pieces. The wall suffers little more than some chipping and scuff marks. Now take a fully loaded tractor-trailer weighing in at 80,000lbs and traveling at less than half the speed of the race car...run it into the same wall. Chances are, you'll be missing a few rows of seats well past the wall. While the front of the truck will sustain damage, the majority of it will make it beyond the wall while displacing most anything in its path until it comes to rest.
The same is true for shooting. A lightweight, thin jacketed bullet at high velocity is excellent for varmints and similar game as you will have the formula 1 effect on them. A heavier, thick jacketed or solid bullet at velocities less than the race car cartridge will retain more of its weight and needed energy to traverse a larger, thick skinned game animal. Energy is just as important as bullet design. Without taking both into account, you set yourself up for failure in the field.
Now back to the 7 ultra. If we are to construct a cartridge for a specific purpose such as long range hunting of whitetails, we want it to deliver a bullet, at a certain average distance, capable of quickly killing that animal. By using the same load and changing the distance to either too far away, or too close, our selected cartridge does not deliver the intended results. Too far and it lacks the energy for penetration and expansion. Too close and it expands too quickly and violently reducing penetration. There is a happy range of velocity for every bullet design.
If all I had at my disposal was a 7 ultra, and most of my shots were inside of 400 yards, I would develop loads closer to the performance of the 7 Rem mag. Why? Because at full capability, the 7 ultra will not perform as desired at those shorter ranges. In my opinion, it is somewhat of a niche' cartridge better suited, at full capability, for distances well beyond 400 yards in the hands of a capable marksman.
I'm sure there are others with a different point of view on this matter. Please feel free to add to the discussion.