I've had this game for a little under a week now and I've enjoyed it. It's not a game I find myself wanting to play for a long period of time, but then it really isn't designed for that. The premise is that you will complete three exercises every day. You can play any of the exercises whenever you want, but you are recommended to play three specific exercises each day, and the choices change around a bit each day. Whenever you want, you can also take a test that will measure your current brain age to see if your regular exercises are paying off. If I don't choose to play extra exercises, I'm usually done for the day in under 15 minutes.
The games are cute, and they don't bore me, but neither would I consider them riveting. Once I've completed my three exercises, I'm usually ready to move on to something else. Note that I have only played in single player mode. I'm sure competing against somebody else would increase the entertainment factor. However, I don't really consider it a bad thing that I don't spend a ton of time playing the game. I do my daily brain exercises, and then I move on to one of the more physically active Kinect games that I find more entertaining.
I haven't had any real issues with the interface. When navigating menus, if you read the manual, it tells you it will not activate any buttons when your hands are close to your body. You move your hand around to where you want it, then push your hand in front of you a bit further to make the program activate the button. On the one hand, I often find myself forgetting to move my hand further out because the other programs I've played with don't require this. But I quickly realize my error when this happens, and one benefit is that I haven't once accidentally selected the wrong thing like I have in other programs. When playing the exercises, I haven't had any issues at all with the program recognizing my movement exactly the way I expect it to. One thing I particularly like is that, while arrowing through instructions or comments, or while scrolling from left to right through multiple screens of choices, the arrow is activated instantly when you put your hand over it. This makes it faster to read through the material. Other buttons have the typical delay while it fills in the little wheel to give you time to change your mind.
Some reviewers have expressed concern that the comments from the Dr. can be overly harsh when you don't do well on an exercise, and that the difficulty can be high for younger children. I can't speak from a child's perspective as I've only played this myself and I'm in my mid-30's, but I can see where some of the exercises would be difficult for a child. That doesn't mean they can't improve if they practice them. As far as the comments go, I haven't found them to be particularly harsh. Usually I've found I agreed with his comments. On the rare occasions when I received an F on something (I'm horrible at that Pacman game!), the Dr. said something along the lines of "I thought you'd be better at this." And I had to agree with him -- I did too! I guess if negative comments from a video game can hurt your feelings, then that's something to take into account when deciding whether to purchase this. But they don't bother me. Yes, my avatar looks sad when I do poorly. But I don't go around grinning like an idiot when I'm doing poorly at something either, so why should my avatar? She perks back up quickly enough after her short moment of pouting.