First thing to keep in mind is the current AR15 is far removed from the Vietnam M16. Also if you ask 20 different people what they think about the AR15 you will get 20 different answers. I will give you my opinion and somebody will disagree and flame me for it. So be it they are welcome to their opinion.

I have two AR's both Bushmaster's. I don't have pictures but I like to keep it simple, all they have on them is a sling and flashlight.

You might want to go to AR15.com and read some of the post. Lots of good info.

Now for the gas piston/direct impingement debate....personally I think the gas piston is a solution looking for a problem. With that said there is nothing wrong with either. If you want a gas piston get an AR that was built from the ground up as a gas piston rifle. They've had some problems with retrofits.

Stick with well known makers....Colt, LMT, Stag, Bushmaster, CMMG, etc. Colt and LMT get the best reviews.

A direct impingement AR will run dirty if you keep it well lubed. There are dozens of examples of 2000 to 5000 round counts on AR15.com. If you clean it after each shooting you won't have a problem. If you let the carbon build up in the reciever and on the bolt they are a nightmare to clean.