Way late to the party here, but just wanted to say how fantastic this custom world is! (I kinda feel weird apologizing for giving mad props to all the creators here, but in a sea of 'issues' I'm hoping I'll be forgiven since there isn't a Kudos folder, that I've seen.)
I downloaded the latest version (because I don't have Pets, namely) and the corresponding save folder, and installation was a breeze, with the city taking maybe taking an additional 2/3 minutes to load, given its size. Upon loading the saved game, you'll be in the Edit Town mode, and if you don't have all the stuff packs/expansions, you'll see a pop up indicating that some objects were naturally replaced. Click the check mark to close that out, and you can pan through the area and see the vast amount of families and community lots that have been so painstakingly added to make the city really fleshed out and seem more like what I envisioned one to look like. From there, you can edit, trim, add at will, then exit out of Edit Town mode and add your family or create a new one.
For what it's worth, here's what I'm running:
Win7 Pro
AMD FX-6300 6 core at (roughly) 4ghz
Nvidia GeForce GTX 750 Ti - only 2gb
12gb RAM
Mad, mad props for a really beautiful creation!
Nano7