NBA 2K15 does not deserves the Mixed (67% positive) review score it's been given. In fact, I believe 2K15 is a huge upgrade from last year's game. Most of the negative ratings given to 2K have been either because players were having opening day server issues, or are running into graphical/gameplay problems. I have experienced neither of these, so here's my review of the game and the game itself
MyCareer - very enjoyable game mode. The story is cheesy in some bits but it's still an enjoyable game mode. MyPark is great to play with friends, but sometimes is lacking on PC due to a reduced community size. Still, fun with others.
MyGM / MyLeague - two WIP game modes that 2K hasn't completely mastered yet but are well on their way. The customizibility in MyLeague makes it a great game mode and it, along with myGM, has lots of potential.
MyTeam - one of my favourite game modes. Challenges, Road to the Playoffs, and Domination give plenty of game modes to play. The auction house is a great addition to 2K15 as well.
Gameplay: 7.5/10 - 2K still needs to fix up the AI of your teammates in MyCareer and non-controlled players in other modes. Online started off sketchy due to server issues but plays well for me now.
Graphics: 9/10 - With a HD 5450 I can run at 60 FPS, 1920 x 1080 and Low / Medium. Don't be fooled by the Low, because the game still looks pretty good compared to last year's game.
Audio: 6.5/10 - Commentary is great, especially with the addition of sideline interviews and the pre-game show. The soundtrack for 2K has been sub-par for a while now but music varies based on tastes. Best you could do is just mute the in-game music and play your own tunes. Problem solved.
Controls: (Keyboard/Mouse: N/A, Controller: 9/10) - playing 2K with a keyboard and mouse is a guarenteed nightmare. I haven't tried it, and don't plan to. However, controller gameplay is easy to pick-up and learn. The shooting mechanism this year is quite well developed too.
OVERALL: 8.5/10 - 2K has definitely created an enjoyable basketball simulation experience for basketball fan. Definitely consider picking it up if it goes on sale (heck, for full price it's still great too). Highly recommend.