Personal - Ridiculously overrated to to point of absolute fantasy, this rifle has formed emotional attachments creating the worst "cult like" followers of any rifle known to the US market. Flawed from the beginning with deliberate (but unplanned for) changes this carbine's direct impingement gas system is prone to reliability problems. While some of the original problems have been lessoned by excessive cleaning procedures, massive training, and modifications (like the forward assist) the basic flaws of this weapon have and will continue in the future to kill fighters fielding this rifle. This rifle is an example of the worst of ill-planned massive kickback programs ever forced on any military. Accurate (in fact it can be very accurate) when matched with the correct bullet to barrel riffling twist rate. Adding a scope to a flat top model can produce an auto-loader capable of hunting ground rodents on par with some bolt action sporting rifles.
Light in weight with low recoil, this rifle can be a reasonable choice for small men, women and children. Similar to the 1911a1 pistol, this rifle designed by Stoner is so common almost any accessory imaginable is available from multiple manufacturers, some practical some downright ridiculous.
I have never had a single version of this rifle that I considered even marginally reliable, I have owned the original Colt SP1, several Bushmaster, and the Olympic Arms made versions. I have never been happy with this rifle's less than reliable service from any of the versions I have owned or been unlucky enough to fire. I have broken parts on all three of the versions listed including at least one charging handle for each example, two extending buttstocks, ejection port covers, and several front handguards.
Function - Will be reasonable, if only marginal, when cleaned and maintained religiously and excessively (the perfect carbine for the anemic mall ninja with obsessive compulsive disorder). Easy to break in the field, will be all but a useless lightweight aluminum and polymer club if contaminated with dust, dirt, or sand. Changing the unreliable gas system for a superior piston type system will greatly improve the performance, but the tight action and twisting bolt head and retainer combination will continue to plague the user with bolt slide function issues. In a short statement - spotless clean and carefully lubricated with limited slow fire this rifle can be minimally reliable, outside of almost pristine conditions this weapon is a liability.
Design flaws - This rifle has a direct impingement gas system that "defecates where it eats" making an already tight fitting easy to stop action super elevated in temperature. Elevated temperatures will cause the aluminum frame to change in dimensions and warp while in use. The tubular bolt travel channel that contains the buffer and spring will not allow for a close fitting folding stock and prevents the rifle from achieving shorter lengths. The charging handle is in an awkward position, hard to manipulate with winter gloves, and very easy to break.
Quality - Many produced are of good quality construction, but the plethora of makers both large and small leads to sub-standard and unsafe products flooding the market. Quality can be all over the map with some surprises, like the original large contractor Colt dropping in quality so far as to be a current joke in the industry. Considering Colt in reviewed comparison to other smaller makers Colt is a third tier choice because of low quality.
Caliber/Ammunition - .223/5.56 is an accurate cartridge very low in recoil, it is often considered underpowered for all but hunting small game.
Use - Accuracy out of the box with a well made example will be better than the average shooter can utilize, trigger can be adjusted or worked by companies like Williams and there are many gunsmiths that specialize in the needed work for higher end target competitions. Can use a detachable magazine that is popular and readily available.
Current Production -Popular and available from many makers and assemblers, fact is you can't swing a dead cat and not hit some maker, seller or shooter of this abomination.
I personally would consider this rifle in the third tier choice, and as a light duty carbine only, any example currently over $400 dollars is far over priced regardless of maker, this is a $350 sloppy, ill performing outdated design that only sells because of the general ignorance and romantic attachment of the typical mall ninja.
I currently do not own one and would never spend any of my own money for one even at 1/4 the current prices - if I were given one I would use it a a possible trade item or for the hunting of small game varmint hunting.