So it's 2010 and the advancements (and understanding) of the AR platform and ammunition vs 10 years ago is lightyears where it once was. That said, has the AR pistol advanced enough to be considered a good option (even in a niche role of PDW?) to be used for serious purposes?

Here's where my head is: I want a rifle, but find handguns to be leaps and bounds more practical than even an SBR for my intended uses if for no other reason than concealability. It's hard carry a carbine and go unnoticed unless it's broken down in which case makes it fairly useless unless you find time and cover to assemble and then deploy it. On the other hand a SBR (pistol caliber or otherwise) with a folding stock might be a better choice but the options there are slim as far as popularity/proven systems that isn't an AK (not that there's anything really wrong with an AK, it's just not a system I'm experienced with). Which bring me back to my original question an AR pistol on a single point sling under a jacket sounds like a good idea to me. I understand that ammo selection is critical but I'm not limited to depending on fragmentation from FMJ ammo as the primary wounding mechanism, I'm just wondering if the short uppers have been improved enough to fill my niche (or if you can think of something that would fill it better).