I love the wonderful combination of left and right brain. Very satisfying to design and rearrange.
Freedom to build city however you like. There is not really any "wrong" way. You do what you want at the speed you want and your city doesn't have to look like anyone else's. (Of course, if you're not satisfied with your progression, there are plenty of people happy to give advice on how to do it differently.)
Beautiful artwork is definite bonus. Poor graphics and animations would definitely detract from the experience.
Wouldn't be here if it wasn't FTP and PvE. Grateful I don't have to worry about my city burning down or being forced to fight.
I entered the addicted/obsessed stage long ago. I'm not going anywhere.
added note: Been playing about fourteen months and am in chapter 9 woodelves (halfway-ish through techs). Playing solo for the first eight or nine months might have held me back, slowed my progression (joined forum at six months while in chapter 6 dwarves), but I have no regrets. Since joining a great fellowship, however, I have definitely benefited from the "extras." Also, I have a *ton* of portal profits because I rarely use them. I see them as a tool to expedite traveling to the next chapter; I get there when I get there and I'm good with that.