Reckon I'll jump in on the fray and add my 2 cents worth here. I have killed 4 deer with a .223. I have witnessed over 6 others killed with a .223. The loads were either commerically loaded with 69 grain boattail hollow points or 62 (I think it was) hollow points.
Before I give my opinion of yay vs. nay, I'll also add, that I'm a heavy for caliber, large caliber kind of guy. A .45-70 does most of my hunting and a .44 Mag is my constant companion. The .45-70 loaded with a 405 grain bullet at 1700 fps, and the .44 is a 300 grain bullet at 1000 fps.
I am not a fan of the .223 for deer. I have seen some remarkable one shot kills and they can be impressive. The problem with the .223 is that it is very erratic. One particular shot may exit, another may not. When they exit it can be a large or small exit wound. If they don't exit, they almost assuredly go to pieces inside and cut everything up. My Dad has killed a buck at 400 yards with a .223. The furthest I've shot one was 125 yards. I've also shot a buck at about 20 yards with one. Not everytime, but almost always (75-80% of the time), it has taken more than one shot to kill the deer. I like one shot kills if I can do them and I have retired the .223 to coyote hunting. It doesn't always happen and even the best of us goof.
So here's my idea, you just bought the rifle. Use it if you can't or don't want to trade it off. If deer hunting in a rifle state is an occasional occurence and you'll hunt coyotes more (legal in IA at least a few years ago, deer with shotguns, coyotes with rifles, still tyring to figure that one out). But if you plan on doing extensive deer hunting, I would seriously consider another caliber. I'm not a fan of the .243 either, but have limited expierience, and prefer the .25s. Use your best judgement. When you do shoot a deer with that .223, shot placement will be the most critical. Keep it behind the shoulder, and as long as that bullet gets past the ribs, you'll do okay.