Admittedly, it is a tough topic--for every hunter that says you should go for more power, there are plenty that will tell you about how they've taken so many deer with it... (personally, I've killed two deer with it--each received two shots although in each case the first would have been sufficient, but better safe than sorry!). So basically I'll throw my two cents in:
I believe that the .243 is an ideal beginner's rifle, useful on varmints as well as deer (with stout 100 gr Noslers or Win PP+s).
Nonetheless, I moved up to a .270 for my day in and day out whitetail hunting for the simple reason that in case of a marginal shot, where a .243 might not do the trick, the added oomph of the .270 would (hopefully).
Last fall I got a running shot on a forkhorn at about 125-150 yards with my .270--I failed to do my job as a shooter and he got away, going to prove that power isn't what kills deer, but accuracy!!
And so, my recommendation to you is to use it all you want to, keeping its limitations in mind, if and only if you can shoot accurately with it.