I wouldn' t hesitate to use a .243 on anything in my neck of the woods. When I was 12, I actually used one to put down a 200 lb wild hog. I don' t know if you know anything about those, but if I (and more importantly at the time, my dad) trust it for those things, a deer is a walk in the park. Like it' s been said above, the nice thing about the .243 is it' s a light, easy gun to shoot with very little recoil. It' s a good shooter to begin with, and it' s so easy on the shooter that you' ll practice more and get better with it than you would a heavier cartridge. Get a good bullet and a good scope, and it' ll be a rifle you take everywhere with you.
If you' re still doubting it, ask yourself if you' d have any qualms using a 6mm on deer. Then remember that a 6mm is the .244. Not that big a difference.