Picked up Cities XL on the midweek Steam sale last week. Very interesting. I like the way I'm not tied to a SimCity grid. I'm a sucker for city builders and I think Cities XL really delivers with the options it has. I do miss the region map because I believe location matters (unskilled workers are not going to commute daily halfway around the world...) but it's a little thing, and for the most part I don't trade workers anyway - it's always easy enough to just build another zone. So far.
I bought Cities XL with the sale on Steam too.
One thing I can say for sure is that relative to Simcity (2000 and 3000, at least), the game mechanics are very simple.
For example, I built a factory next to a farm, and the farm suffered no ill effects. I intermindled residential, commercial and indutrial zones, and put low skilled and skilled housing next to each other, and the only warning I got was that people were having a hard time moving into the city.
In simcity, doing those kind of things made people move out, not try to move in.
Another member suggested mods to change the gameplay, but so far, all I've found are building mods.
If I understand correctly, it was orignally a multiplayer game, which could explain why it's so simple relative to the single player SC games.