I was always disappointed by how the computer calculated if people could get to work or not. Had a system where everyone was in small grids scattered, and the had to use the underground to get out of their grid, then a bus to get to work. It would work most of the time, but randomly it would fail. Very good for income though:)
I had a setup once where my income was out the roof so I decided to put industrial buildings on the far outsides parts of the city raised the middle sections and put a cross tunnel with residential on top of the raised area...it was weird...
Anyways those two sites are always reliable and adding new material.
I'm working on a Siberian mega city, but for some reason it's not working as well as other cities I've built similarly.
Both the sites I mentioned above have mods and new buildings (landmarks, utilities ext.). Also be sure to download the NAM, besides it being just as big as 4.85. (Bout 85Mb)
If you're going to download CAM, make sure you have a hell of a comp. The mod size is 2GB unzipped.
Freelancer and Sim City are both games that keep me up past 1. Too addicting.
Note: at one point before my hard drive went I would play with 4GB of plugins.
As for mods, so easy to build up incredible amount of 'em. Always wanted to get the monorail embankments (I think it was) to work, but it needed so much work. The waterfront ones are a really good set too, again, if a bit clunky.