As the owner of rifles chambered for 308, 30-06, and 300wsm I can say that the short mag definitely has its place. Someone earlier called the short mag a handloader special and I agree with that. The design of the brass was tailor-made for reloading. A thick web, little body taper and steep shoulder angle provide brass that lasts many, many firings, even pushing the limits of the cartridge. I bought 100 pieces of Norma brass when I bought my M70 in 2004 and I am still using the same brass today.
The short mag in my experience is very easy to load for much like the 308. Nearly every recipe I have tried shows a definite node near the top end and when you find the node the accuracy is nearly unbelievable for a hunting rifle. In terms of velocity I get 3300FPS with my 150gr load, and 3100 with my 165gr load, both using IMR 4831. I have not shot game with the 165 but the 150gr load is a hammer on whitetails unlike any other rifle I have used.
As far as availability, the shortmag is not going anywhere. With the younger generation it is a popular round, and hell, you can still find ammo for outright flops like the 225 Win and 6mm Remington 50 some years later. Every major rifle manufacturer has made WSM rifles, and from what I have seen all of them except Ruger have current models so chambered. The WSM has made it 14 years and it's still selling rifles folks.