The drawback is the Sims that need to find work outside of the towers, as well as freight supply trucks for the commercial businesses, generate massive amounts of traffic routing to and from the towers.
The advantage, though, is that with the 8 levels that can be built, they house massive amounts of Sims, and can include a school, negating the need to build schools, plus commercial shopping all within the same footprint.
They also have enormous footprints in cities that have always been too small. They are expensive to build, and take a significant amount of time to start generating revenue. These are specialization buildings like the casinos, or resource operations. This expansion adds two new ways to play the game, whether by adding futuristic towers of apartments and shopping malls, or giant corporate towers.
