Once I figured out that splicing a new job that required land gave you a new building, and that the buildings would unlock abilities(like the bank that gives 2x to a fully staffed building or the observatory which lets you change the background), I got hooked. Also trying to figure out which to splice to fill the jobs needed to fill my buildings is pretty fun. So far the only u-points I've spent have been on 'decor', which gives you % decreases in the wait time on splicing and building, and trees that give you coins and the occasional u-point. I also enjoy the city planning aspect of the game. I feel like I should mention, I haven't spent any real money on this and don't plan on it. I read a review saying that after a few days it becomes necessary to use real money to acquire more land(in lieu of waiting multiple days coin generating), and if that is the case I'll probably stop playing.
Here's a quick and dirty shot of my town so far.. which was kind of planned as I went along, hence my desire to restart.