It's a great all-around cartridge for varmints and game animals up to and including elk. Very flat-shooting, gentle on the shoulder. It's ideal niche is deer and pronghorn. For varminting, it's a bit much on recoil and muzzle blast to tolerate high volume shooting like you would encounter on a busy praire dog town (200+ rounds in a day). For large elk, proper bullet selection and good shot placement is a must, since the lighter .257" bullets are unlikely to penetrate the heavy shoulder bones of these animals.
A .25-06 was my first rifle, bought on my 18th B-day. I've used it for praire dogs, coyotes, pronghorn, deer & elk with great success. However, I now have dedicated varmint rifles (.17 Rem & .220 Swift) and a much more potent elk rifle (8mm Rem Mag) to give a greater margin of error if I find myself facing a very long shot on a very large animal. The .25-06 is still my primary deer and pronghorn rifle, though, and also gets carried for cow elk.