I think it is a well designed cartridge, and I like the rifle, but here are some pros and cons, btw, I'd like to have one myself:
300 RCM
Pros:
Comes in a nice rifle
Can approximate 300 Mag performance with careful handloading
Lighter than a 300 Win Mag in the same rifle
Better cartridge design than other short mags for easier feeding and extraction
Cons:
Brass is really expensive and you'd have to stock up
Only one manufacturer of brass
30-06 and 300 Win Mag brass is cheaper and available everywhere
Way better rifle selection in 30-06 or 300 Win Mag
Is a little faster than the '06, but not equal to the 300 Winchester Mag
You can find '06 and 300 Win Mag factory ammo everywhere, you'd have to stock up on factory ammo if you wanted it
300 WSM does everything it can and brass is readily available from multiple manufacturers
300 WSM rifle selection is also way better
