I'm not a huge AK47 fan. For a deal at the MLE or less, he can help a team. However, I don't see him as a star.
My three biggest problems with him are: 1) he's mentally weak (breaking down in tears in the playoffs, threatening to return to Russia); 2) he's the first guy out of the gym (according to Deron Williams); and 3) he's concerned about his own stats, and is a bad teammate (according to Deron, and showcased by the fact that Deron, ownership, and the coaching staff have all called him out).
Plus, his stats have basically been in decline for several years now; he doesn't bring the same energy he used to, and perpetually seems to be sulking. Also, if he's not in exactly the right system, he struggles.