The main utilities I see for ICS in this game is for two things: Rapid army rush-purchases, and more rapid growth.
The army rush speaks for itself and has been discussed here: the more cities you have, the quicker you can purchase a huge military if you have enough gold.
The other real use here is that the more cities you have, and the sooner you have them, the faster your population (and thus worked tiles) grows. If you're going for the megacity like MKElderGod is talking about, the faster growth translates to faster worked tiles in the megacity as you buff it up.
However, this does not mean it's any better to pack these cities in overlapping areas to start with. Sure, expand the number of cities as fast as you can, but its silly to not spread them out at the beginning. By spreading out, you ensure that you grab good resources and (more importantly) choke points and blocking points, which deny your competitors access to expand toward you. You can fill in the distances between with more cities later, and even overlap cities' tile areas if you feel you need your population to grow that much faster. But with roads making instant movement between any two cities, why start out packing your cities together?
A disadvantage I have found from having too many cities in Civ Rev is that it can actually slow your military movements. Many times I have found that roads in a certain direction will only go through a single city, and there is not the option to build roads around it to the cities beyond. Each time a military unit travels through a city, it loses a movement point. I had a game where I was trying to send tanks to my battle front against the French, but it was taking many of them 2-3 turns to even get there because the only way was through cities along the way. Before I had ICS and filled the holes in my land, my troops were able to make it to the front lines in 1 turn, from anywhere in my empire.
Just something to think about. ICS isn't nearly as powerful a strategy in this game as compared to previous ones.