Nothing wrong with the .30-06. It's been effectively used to kill pertty much anything that walks since you great-grandfather was in diapers.
Seriously, the .30-06 is a great intermediate .30cal round that is appropriate, with the right bullet and load, for all game up to and including moose, given that you limit yourself to reasonable ranges and pick your shots wisely.
It's an excellent long range deer cartridge, and a very good moderate range elk gun. I, personally, would choose something a little heavier for anything bigger than elk, perticularly dangerous game, but that's not to say that the '06 won't do an acceptable job if you are a diciplined hunter.
There's a good reason that the .30-06 is among the top three most popular cartridges in the U.S. and very popular throughout the world. There isn't anything romantic or exciting about it, but it is cheap, available and just plain WORKS.
Mike