Jack, those are pretty much the same purposes I have my AR-15 for. Something to tote around with me when I'm back in South Carolina walking around in the woods when it's not deer season to blast coyotes with and such, range work, and defensive use. I placed a little greater emphasis on defensive use, perhaps, as I initially bought it for my dad and it was going to be his only rifle, so I wanted it as bomb-proof as I could get it. But he ended up buying his own rifle before I could finish building it (it was going to be a surprise). Hehe, I had been working on him for years trying to convince him to get a rifle.
I found this very illuminating post by DPMS, while searching around:
http://www.ar15.com/mobile/topic.html?b=2&f=30&t=201191
Doesn't look bad at all. From what your needs sound like, it might be worth considering.
Do give it a good, thorough look-over before you do buy it, though.
If you can field strip the rifle and take a peek at the bolt carrier (only takes like 10 seconds), you can check that the gas key screws are properly staked like the photos in the linked thread. It'd also be a good idea to inspect the bolt itself and make sure it has no cracks or broken lugs or anything.
Switch the safety back and forth a couple times and make sure that it has smooth engagement and disengagement, and that the detents hold it into place in each position fairly well (if you need to replace this part, it's cheap and no biggie, but if it's not right you could use it as a bargaining point).
Check that the safety works, when off it should drop the hammer, when on it should restrain the trigger.
Check the mag catch and magazine function if possible. Do you plan to use USGI (aluminum) magazines or PMags? If you plan to use PMags you might want to see if you can get your hands on one to check fit and function for. Sometimes the magazine well dimensions or mag catch might be a little off on various makes of AR-15s, but all should at least work with the USGI mags.
Check the bolt movement by lowering the bolt with the bolt release and cycling it a few times with the charging handle. Does all feel smooth? Is there any binding?
Inspect the hammer and trigger pins on the lower receiver (don't remove them, just look at how they fit in the receiver holes, they're the two holes above the trigger area in the following drawing). Try to wiggle them around a little from both sides. Are they very loose, or is the fit reasonably tight? Ideally you don't want too loose of a fit, here.
Inspect the front sight assembly. Try to wiggle it side to side, front to back. Is it loose at all? Does the fit to the barrel appear to be good? You want this to be rock-solid tight. Is it canted significantly one way or another, or close to straight up relative to the receiver?
Inspect the flash hider. Does it look straight, concentric to the bore?
Inspect the buttstock. Can you turn it with hand strength, by grabbing it by the butt and trying to rotate it along the axis of the bore? If so that's not a good sign.
Check the weight of the rifle in your hands. Some AR-15s have very heavy barrels, others have very light barrels, and everything in between. This will affect the balance, handling, and carryability. A very heavy barrel is good for competitive shooting, mag dumps, and full-auto fire, but isn't that great for a field rifle.
If all of those test alright, it might not be a bad choice. Throw in a couple spare parts to carry around with you as backups in case something goes wrong and you'll be good to go:
Spare firing pin:
http://www.bravocompanyusa.com/Firing-Pin-AR15-p/firing pin ar15.htm
Spare bolt (whenever they're back in stock, BCM has email alerts):
http://www.bravocompanyusa.com/BCM-AR15-Bolt-Assembly-MPI-p/bcm bolt assemly mp.htm
Maybe add a MagPul MIAD (adjustable, about $30) or MOE (nonadjustable, about $20) grip (BCM and Brownells have 'em), and get the optional core that stores the bolt and firing pin for you:
http://www.brownells.com/.aspx/pid=26689/Product/AR_15_M16_MIAD_trade__GRIP_CORES
Keep it lubed with SLiP 2000:
http://www.bravocompanyusa.com/SLiP-2000-EWL-p/slip2000 60320.htm
http://www.brownells.com/.aspx/pid=41759/Product/SLIP_2000_LUBRICANT
A bolt action wouldn't be a bad choice, either. I keep eyeing those CZ 527s, they're made both right and left handed...
http://www.marlinowners.com/forums/index.php/topic,88120.0.html
I have a CZ 452 American (.22LR) that I picked up fairly recently that is just amazing and is fast becoming one of my favorite rifles to shoot at the range. And it sounds like those .223 CZs are every bit as good. Then of course there are also always Savages, and Winchester (c/o FN-Herstal) is back in action producing M70s in Columbia, South Carolina (only right handed versions), etc.