I am a huge fan of the 30-06 and the entire family of cartridges. I am building a 280 AI, I own an 06, 25-06, and 270 already. 270 was my first love and has been in my "stable" since I was 21, I've stated that on the forum before. With the right bullet it is the hammer of thor on deer and antelope, will work very well on elk under 300-400 also with the right bullet.
If I am forced to choose only one for hunting everything, right now, it's the 30-06. We shall see after I finish the 280 build!
I would also add that my 25-06 is my favorite for deer and under game. It's a laser, shoots sub .5 MOA with factory Barnes Vor Tx, and I have only had one animal walk more than 50 yards on me once the trigger is pulled, that was a Wyoming antelope with a high double lung shot. She ran a quarter mile semi circle, my walk straight line to her was less than 100 yards.