1. There is an element of surprise, good and bad.
2. Challenge. For example, collecting doesn't consist of camping the very same spots over and over again, save after save. Sims are required to explore.
3. It's not the Truman Show. NPCs don't exist in order to fulfill every whim and desire of the played Sims. Time actally matters because everyone has something to do or someplace to be. They're not sitting around waiting for player Sims to show up.
4. There is intimacy and genuine affection in relationships (though not as much as TS2).
6. There is situational awareness.
7. Traveling to other worlds actually feels like a getaway -- new Sims, new sights, new types of adventure.
8. Venues are fun to create and to visit. There is much more freedom to choose objects and Sims will use them according to their personalities. Also, when you place an object, NPCs show up automatically, no matter the venue type. No immersion-breaking necessity to hire staff.
9. Sims don't constantly interrupt dates, meals, and family outings.
10. The worlds aren't finite and identical for every save. Starting a game in a new world truly feels like a new beginning. Because of CAW, the possibilities and re-playability are essentially endless.