About 5 years ago I had the chance to shoot 2 seperate barret 82's. I had the bug bad and wanted a semi auto 50 REALLY BAD. Well, thankfully, I shot 'em before I spent the cash. Accuracy was dismal! 3+ moa was the best I or any other shooters could do. I have been told that accuracy has since improved, but I cant verify this from personal experience.
My thought at the time was, why get something that can shoot for miles if you cant hit it? So I tabled the 50 idea.
About 7 months ago, I got to shoot a Barrett 99, a Serbu, and an FN 50 ( forget the model #), accuracy was good 1.5 MOA or less with ball and the bug was back. I mentioned my desire to a range buddy/FFL here and he invited me to shoot his AR-50. Up to this point, I was pretty settled on the Serbu, as it seemed the most accurate for the $ (the FN gun was nicer but VERY expensive, nothing wrong with the barrett, but why spend the extra $$ if you dont have too).
Well, after shooting the AR-50, I had to have one. Yeah, its not perfect - its HEAVY, the trigger while crisp is heavy at 4.5 pound (and if you mess with it you void the warrenty and yes, per a source at Armalite they weigh and record each rifles trigger pull before they ship), and to fit it in a case you have to remove the back of the stock.
Plus side is it has very little recoil (less than a 12 with heavy loads to me) and its accurate as hell! I have 3 friends with AR-50's and all shoot MOA or less with certain flavors of ball. So in my opinion Armalite is putting out a fairly badass package. It would be better if they had an adjustable trigger that was lighter, but this is only in development stages for now. Lighter and a folding stock would be an improvement, but you cant have it all.
Yes there are better, slightly more accurate rifles out there, but unless your shooting in long range matches , eg 1000+yards does the difference between .5-.6 MOA to .4 to .3 MOA justify the increase in cost? Only you know the answer.
Hell, if your located close to OK, you can come shoot mine.