I have a DB upper in 300 AAC I got back before the holidays and have put about 150 rounds through it (can't find the ammo to shoot more. You think finding .22lr is hard!). Shoots fine and it's almost impossible when shooting the gun in 5.56 to tell the difference. I just need to remember to keep the mags with the AAC separate from the ones holding 5.56 ammo. At first glance it's hard to tell which loaded magazines are which unless you know what to look for. A great caliber with the potential to take over as the main rifle round for the military/LEO community with minimal expense... essentially you simply replace the barrel on the current M4 and other 5.56 chambered guns.
FWIW, I own a LARGE number of guns (probably more than most of the local gun shops) and have been shooting/buying firearms since I was a teen in the 1960's. Some of my biggest lemons have been high end, "name" brand rifles and handguns while some of the most accurate and/or reliable firearms are some of the least expensive and most maligned.
Honestly, if I avoided every gun that's received a negative review or caused somebody else a problem, I'd own nothing but a crossbow and a slingshot! My advice is get the gun you want, then go out and shoot it. If it works the way you expect it to and are happy, the gun's a keeper. OTOH, if there's a problem, either fix the gun or get rid of it.