Personal - I have never joined the cult of the M1a rifle and feel this is an acceptable rifle with the same limited choices in bullet weight and performance choices as the M1. If anything the M14 is and was simply a product-improved version of the M1 Garand with all of the features the M1 should have had for WWII. The M1a is typically overrated with an emotional nostalgic attachment that is equal to or worse than the cult-like attachment HK owners are accused of for the HK products. It has, or can have a nice wood stock, particularly the multi colored laminated wood, I am partial to the old-world wood stocked rifles myself (while this has some limits I do like wood it is my personal romanticism).
I feel the attachment to the M14 is more of an american reaction to that abomination of the M16. My personal distaste for the M14 and M1 type rifles has more to do with the politics and cult-like romanticism in the background and the incessant ridiculous psudo-patriotism far too many shooters wrap arround the rifles and pistols that they think represent 'merica. That puffed up ignorant joe-six-pack attitude I find distasteful and it transfers to the items themselves because of that.
The fact is the M-14 lost to the FN FAL in the weapons trials (and for reliability the G3 would beat the FN FAL). The Army rigged (more closely ignored) the testing to accept the far second place entrant, lied to procurement that the same tooling could be used and generally showed a terminal case of not invented here. This was all for naught as later the wiz kids under the corrupt McNamara choke down our soldiers throats that piss-poor abomination the M-16.
I would without reservation say that the M-14 is far more reliable than the M-16, certainly far more powerful and rugged. The politics (and probable kickbacks) only prove that our military leadership does not care that much for our soldiers, what else would explain the resistance to the far superior rifle designs available now? We spend almost two billion a month in the sand box, but the Army cannot afford to supply the troops with a GOOD rifle? We could resupply with new rifles for what it costs for a few days in-country. It's like someone blathering about how good that Garand rifle is, and how great it shoots with that "gift from the gods," "the best ever" cartridge the 30-06... While they most likely will also tell us that "we don't need no 'ssault weaapeeon" to go hunt'n wif...
We all know the facts point out that the .308 (in and of itself) is inherently more accurate than the 30-06 in the same conditions.
Function - Can be excellent when clean and properly maintained, in fact it is often a bit more tolerant of fouling than its father the M1. Like its father it works best within a limited set of ammunition parameters, outside of the narrow choices it tends to be problematic. Same as the M1 this rifle has an open action that can allow contamination.
Design flaws - Operating rod is prone to damage, but when compared to the gas impingement of the M16 the M14 was heavy but reliable. "Tuning" for accuracy will only last for a limited time and the rifle will pound the receiver with enough force to knock out any adjustments and fine tuning often forcing the user to re-glass the receiver. Cleaning from the muzzle is always a PITA. Possible slam fires caused by the free floating firing pin (never observed this myself). Modern manufactured cast receivers are not as strong and resistant to wear as the hammer forged originals or machined examples. The M1 Garand and the M14 designs use a free-floating firing pin inside the bolt head/body. When the firing pin channel is filled with fouling, the firing pin may lock in position protruding from the face of the bolt. The weight of the firing pin alone can also be enough that with inertia it will deform the lighter bodied primers and fire the round - this can cause a slam fire or out of battery fire both very dangerous the second catastrophic. It is strongly suggested to use thick military grade primers and or military surplus ammunition not the thinner primer charged civilian ammunition.
Quality - Most produced in the US are of good to excellent quality, I have heard of QC problems, but personally the examples I have owned and others I have used (all US made) were of good to excellent quality in construction and finish. Some reports of problems with the limited importation of the Asian made rifles seem to be repaired with a new proper heat treating.
Caliber/Ammunition - .308 an accurate and effective cartridge, one of my favorites, but is large and some consider it excessive in recoil (I do not). A good general use cartridge that crosses from defense, to hunting and good results even in many competitions.
Use - Accuracy out of the box will be better than the average shooter can utilize, for a good shooter this is mediocre to reasonable. Trigger can be adjusted or worked by companies like Williams and there are many gunsmiths that specialize in the needed work for higher end competition - and it will need a lot of continuous attention. This rifle can an use a detachable magazine that is popular and readily available at reasonable cost. The M14 can produce reasonable to excellent accuracy when maintained regularly. Similar to the M1 the op rod design has a tendency to "beat itself" out of its own narrow range of higher performance and accuracy. It takes a lot of continuous work and repair to keep to higher accuracy. Just like the M1, the M14 is often slathered with automated patriotic credit in the shooting community for accuracy and reliability that this rifle design does not deserve nor has it exactly earned without extensive modification. Like the M1 rifle the adjustable iron sights are excellent almost to the level of many available speciality competition target sights (it takes some time to learn to utilize all of the features).
Current Production - Popular and available and many of good to excellent quality in production from several manufactures in the US.
I personally would consider this rifle a primary choice for a current MBR, with many quality examples available, with only the high price and design limitations a possible concern.