I don't dislike them or have anything against them, but I have a few of reasons for not owning one. The first is that I have yet to find a comfortable AR. I've shot a few and handled many, many more and I haven't found one that pulls up to my shoulder and finds its niche easily. That's not to say that I couldn't, but I just haven't. And I figure if something isn't comfortable for me, then it's just going to sit in the cabinet.
The next reason is cost. I know you can find a $600 AR from Walmart or catch a cheap one on sale somewhere, but you really need to put a pretty significant chunk of change down to get yourself into a decent AR with good optics. Heck, a good set of iron flip-up battle sights alone will run you $100. I'm sure if you were really frugal and took your time you could build an AR for $500 with everything you'd ever want on it, but I think there are better 'out of the box' rifles around in the $600 price range. I just bought a Mini 14 Tactical (not the ATI-Stock version) for $600. I couldn't find an 'out of the box' AR that I loved the way I loved the Mini for that price. I did consider spending a few extra bucks on an SR-556 though...
The third and final reason I don't own one of the 'black rifles' is my wife. She's very timid about guns. In fact, she doesn't like them at all. She doesn't mind me having them and doesn't mind me having a shooting hobby, but she's not a fan of it at all. I was discussing AR rifles with a friend at church that shoots a good bit and she got a little weirded out by that gun. More so than others. She is of the understanding that an AR is a fully-automatic assault rifle. I guess she's seen them in movies and on TV and the news and she's just really turned off. I'm pretty much able to own whatever guns I want within reason so I don't want to stir the pot by buying a gun that I don't absolutely love.
I know that ARs are great guns and the SR-556 is a tempting rifle, but for me, it's not something I lust after or look at a whole lot. Seems the whole gun industry has gone tactical and I just prefer stuff that's a little more clean and classic (not wood, necessarily).