I don't own one, (the AR bug bit me before it was introduced); that being said, there's nothing wrong w/the Sport. If they had existed when I decided I needed an AR, I would more than likely have one. I will leave you with the advice I used to give when I worked at the LGS: in re AR's, if somebody builds exactly what you want, buy it! If the first thing you're going to do is switch the buttstock, pistol grip, sights, etc.; you're better off building your own. I bought one, (M&P 15 MOE), and built two, (both on S&W receivers).
-Klaus