The author does a fairly decent job of giving an overall rundown for someone that is looking to get into an AR. There is really much more than most will every get into. The size of the gas port has as much to do with the ideal buffer weights and BCG as the length of the gas system. Most of the economy models and entry ARs tend to be extremely overgassed. This allows them to function (though maybe not ideally) with just about any crap ammo someone will throw through them. This along with overall quality of the parts also leads them to be more prone to breakdown when run hard.
Mil-spec as a standard should be the minimum quality acceptance level. It is not hard to purchase/assemble a quality rifle well in excess of mil-spec quality. For example accuracy for true mil-spec barrels is really not that great...you need to know which mil-spec you are meeting.
As an aside the final AR derivative that Eugene Stoner worked on and his idealized design is the SR15 by KAC. He determined the ideal gas system for the 16" rifle to be a proprietary intermediate length gas system (a bit longer than mid length but shorter than rifle) and it uses a Full Auto(M16) BCG with an H buffer as the standard. The KAC SR15 is considered one of the best, softest running most reliable ARs available.
He is somewhat correct about assembling ARs. I cant tell you how many rifles I fix from people who "can assemble a rifle as good as a DD, BCM, PWS for $6-700". Understanding how the components work together is important when deciding what to use....not just what is on sale. If you start with and use quality parts you are more likely to have a god result. Generally with boutique brands like Radian, Modern Outfitters, Noveske, Triarc, you get a very reliable gun with excellent fit and finish made from parts that are generally much better than mil-spec. Sometimes a manufacturer will get too cool for itself and build the "the best rifle ever!!!" and they will look great.....and run like crap (see Era3 and Salient). To an end user the major difference between a quality production gun (Colt, BCM, DD) and a higher end gun (KAC, Veske, PWS) is not going to be in reliability it is going to be in the inherent accuracy of the gun and long term durability. It is up to the owner if the price tag for that is worth it. One good thing is that even the prices on these guns are coming down somewhat in this soft market.
I have personally owned and or built over 30 different ARs. I work as a gunsmith assembling, repairing or "fixing" them daily. I have been to Colt and KAC armorers school. The heart of the rifle is the barrel and bolt. These are the most important items to put the money into . As Jackalope says you can build a decent, hell even a very good rifle, just make sure to take the time to do it right.
