We're playing today more now that it's a holiday weekend. He completed one mission yesterday and one this morning... I really like it! It's stretching DS which is perfect. For example, this "mission" is about orders of operations. They have been very clever about how they created the game so for example, this one flower "pod" is an expression like 5 x ((10+2)/6) + 2 and you have "charge" each branch of the pod. Each branch would be some sub-expression like 10 + 2, 12/6, 5 x 2, etc. BTW this is given after your in game companions introduce the concepts so it's not like you're expected to know it right off the bat.
The journal entry is some very basic written text that describes the concepts currently being covered in each mission. I do have to help every now and then and explain something in more detail. But in general, the boy is getting it. I am sure it will take some repetition for him to have mastery but a) in the school systems when he'd get to this level, he'd be getting full blown instruction by a teacher, and b) he loved Timez Attack so much I know that he'll play and re-play the missions over and over again. Really when I jump in to help DS it's usually more about helping him find the next widget in the game or find the exit.
The only negative is that the game is a little choppy on the laptop that we have set up for the kids. On the Mac Mini it's great (but that is currently set up in my office). I may let them "borrow" the Mac though. Make sure you play the demo copy to see if performance is acceptable on your computer.
Very happy with the purchase otherwise.
JB