Really good game, not so much different from SimCity DS but the differences make it better than the other. The evolution of the city through the ages is incredible, the challenge mode could be rather difficult sometimes, but it's fun all the time.
The only bad thing I have found (not really bad, but I have great memories of it in SC3000) is the lack of subway system. I am not in the last age yet, maybe the subway system is available then, I do not know.
Anyway, a great purchase if you like this kind of simulation games.