Thanks for the input, drck1000. If I decide to buy a basic first gun, would a Colt 6940 fit the bill, at least until I figure out what I really want?
If you want a gun that
is 100% MILSPEC,
has a monolithic upper,
has a free-floated barrel,
is the one brand Law Enforcement trusts to require their officers carry in many places (including Hawaii),
is made by the company who made the M16A1,
owns the patent on the AR-15,
makes the M4 for the military,
doesn't have the A2 front sight / gas block,
has a quad-rail,
and has good resale value
then a Colt is the one to get.
The quality of cheaper, well-known and respected brands is often just as good as the Colt. Depending on the features you find most important, another may be better.
I think if your budget is in the price range of a Colt LE6940, it's a great first AR. You can trust the quality, take time to learn about how it functions, add a few accessories if you like, and be very happy for a long time shooting it.
One day, when the bug hits you, you'll want to build your own. That may exceed the cost of a Colt, especially if you buy all the tools versus borrowing, but you'll understand how the AR works best by building one that works! In the meantime, you won't be disappointed with the Colt.
I believe mine was about $1,500 just as the Sandy Hook craziness started. I've added a light, Aimpoint PRO red dot, B.A.D. lever, Ambidextrous safety, an Angled Fore Grip, and a MIAD pistol grip.
If I knew what I know now, and if they had been available at the time, I would have been happier with the Colt OEM2 model. Buy the gun, pick your own furniture, and save money. I'm a fan of low profile gas blocks with a free-floated barrel, which the OEM2 offers. This lets me use a longer hand guard which pushes the front sight more forward for a longer sight radius.