The few primary units I've handled and owned were pretty good. Having said that, I thought the included FTS mount was junk. I have heard of a few other brands being OK(as well as you probably have - like vortex and burris (i think)), but never heard anything about the mounts.
I always wanted a larue mount for mine, but often wondered if it was even worth it (like parking a ford pinto in a garage meant for lambos and ferarris). I knew that eventually I'd get tired of the weight and crappy mount and just ended up with an ACOG.
I'm not bashing this setup though. I really liked mine. I think the higher quality stuff (like the larue mount and an aimpoint mag) would have been sturdier and lighter and I may not have been shopping for something better. When reality sets in (and the price of it) - I realised that an ACOG was around the same price as my dream combo (M4s, aimpoint mag, larue mount) - and truth be told I really wanted one anyway..... and you see why I did that.
Comparing the setups...
The M4s was everything I ever thought a red dot could be.
Flipping the mag into place, I had honestly hoped for a little more clarity, but looking through that many lenses will do that. It was decent, and only the pickiest shooter would dislike it (I was ok with it).
The results were ok too. I went from hitting bowling pins at 100yds with ease to picking off golf balls most of the time at that same range(I could atleast make them dance and roll around).
The ACOG (that you didn't ask about) - does all that, but clearer and better - but not without some tradeoffs. Shooting into/out of different lighting situations can be a challenge (or require a glow stick). Close and fast work takes some getting used to as both eyes have to train to superimpose that chevron on the target.
In summary - I think the PA stuff works ok, and you'll be happy if you change the mount.
A good solid light weight RD/mag/FTSmount makes a great do-all rifle in my opinion, but like most swiss-army-like stuff it won't do all of it the best.
Sorry for the story... but I thought I'd share my evolution through these parts. Maybe it will help confuse the situation a little.