Cities of Tomorrow isn't a bad expansion if you're already a big fan of SimCity and are itching for new ways with which to test your city-building skills within Maxis' sandbox. The new facilities add alternative approaches to creating prosperous cities of utopian wonder or unbridled capitalism. They can be appealing and even fun to experiment with, as long as you're not hoping for this to do much more. On that level, Cities of Tomorrow works decently well. If you're expecting it to solve some long-standing issues, there's nothing to see here beyond the neon glow of the streets and the purple haze hanging above every smokestack.
As a D&D and Neverwinter Nights fan, I wanted to see what an MMO version offered, and I came away feeling that it accomplished its goals, if only for a month or so. It's like a single-player sandbox dungeon; when I reached what felt to be the proverbial end, it was time to move on.