I have almost 1000 downloads for this game. It all depends on what you want to do with a region.
If you want better transportation and transit options then download the nam.
If you want more realistic cities, I suggest you download some W2W buildings which can be found on Simtropolis.
There is a lot of different scenery mods that deal with terrian, rocks, water, and trees.
For realistic waterfronts, there on many different downloads where you can get seawalls or canals is you want a Chicago loop type of city.
Also if you want big towers, search for top rated buildings and you can find some. There is a few from Toronto, Montreal, and Calgary. My favourites are the ones where you can plop them into the city and you can still get jobs from them.
Last thing is if you want to have fun without worrying about your finances then download the money tree. That way you can increase demand by having your taxes very low or even at zero.
On another note, I used Sim City 4 on vista and never had a problem. I'm currently using it on Windows 7. It just takes 10 minutes to load because of all the add-ons I have. Sometimes my game will quit on me but it's not very often.
Hope you have fun.