I have three of them and 80% of my hunting has been done with a .300 MkV Wby that I bought back in the 1980s. That said, it isn't perfect, and other calibers have attractive characteristics too.
YMMV, but for me, the .300 Wby took a bit of work to master. Everyone has different recoil tolerance but it took me many years to learn to actually shoot it well. Before I went to Africa the first time I dedicated a winter to learning how to shoot it and put several hundred rounds down the tube. For me, personally, it's the upper limit of what I can shoot comfortably without flinching. The single biggest drawback of the 'bee is the recoil. As others have said I have zero, ZERO interest in shooting with a break. The muzzle blast is as noxious as the recoil, and even worse for people standing next to you. I've already lost a bunch of hearing from shooting. The round isn't particularly efficient and requires copious amounts of powder to generate the velocity it does. The huge freebore of the MkV is counter to what most people would design for accuracy (but mine is a genuine 1/2 MOA shooter with 180 TTSX). As you say, it's perfect for elk to 600. The Barnes do tend to foul a barrel, so there's always that to fight. In a match barrel, that would probably improve.
Weatherby magnums tend to have a poor reputation with outfitters (worse before than today) and I just don't think most people shoot them well. A shot from a canon through the guts or a hind leg is still a problem. Most people are better served something in the .270 or 30-06 class. My PH in Africa carries a .308 as his daily medicine for the occasional lion and leopard and does not consider himself to be under-gunned.
When I decided to have a custom build, I went with .300 Win. It's easier to true up the action, easier to fine tune, easy to find brass, slightly slower, and I built it with an Ultra 5 Thunder Beast can. It's an absolute joy to shoot, it's a reliable 0.300" shooter, and it's my new go-to gun with 190 HVLDs. I'm comfortable on elk to 800, deer to 600, and steel out to 1000.
YMMV.