With good bullets, and a man who can shoot, your 30-06 is a 500 yard elk killer. The 300 WM extends that range up to 550 or 600 yards. At ranges out to 400 yards no animal will ever notice the difference between the 2. Between 400 and 500 yards the 300 mag might offer some advantage, but not much.
I'm not opposed to using a magnum round if someone wants to. I own a very similar 300 WSM. Shooting game larger than deer at extended range is what they are made for. But for most people, including me, a 308, 3006, 270 or any of about a dozen other standard cartridges are more than enough.
The question is, are you good enough shot to take advantage of it? The added weight, increased recoil, more expensive ammo are also things to consider. Only you can decide if it is worth it to you. If recoil doesn't bother you and you can shoot it well the extra power never hurts.