I've almost purchased an AR-15 in .223/5.56 about 100 times, but no matter how bad I want one I keep coming up with the same conclusion. They seem a pointless waste of money.
1. Too small to reliably hunt medium-large game (.308, .30-06, etc. more practical)
2. Not really meant for long range (.308 or 6.65 more practical)
3. Can require close range/precise shot placement to hunt large hogs
4. If you don't hit your target in the first few shots you likely won't have anything left to shoot at anyway, so why 30 rounds?
5. Shotgun with birdshot and slug mix is a better/safer home defense option
6. If they (or their ammo) are outlawed you can't legally shoot them at ranges or use them for hunting. Not sure what happens if you use them for self defense. It's great to be alive, but then what?
7. The ammo is cheap, but .22LR is cheaper, plentiful, and legal
I then looked at AR-10's, but with their weight at full capacity and expense (purchase price, ammo) I just decided I'd stick with traditional hunting rifles.