The server loads arent an issue anymore (most of the time anyway). It's the flawed game simulation. The traffic and economy are just pure crap. For example, person moves to your city, they pick the closes house to them on the road. Then each day they go to work, they go to the closest place that has a job, then on the way home, go into the closes house. So no sim is ever at the same job or house.
Then theres the fact that you can basically fill your city with just residential (no services, government buildings, etc) and you keep making money, despite the sims having no jobs, and your city burning down.
Very flawed game logic.