I'm definitely on the fence about TS4 after about 4 hours of game play. I like the emotion system and some of the new features but I feel like they came at a pretty high price, namely very limited towns and build/buy/wardrobe options. To be fair, I started playing TS3 after Late Night came out, so perhaps the base game was equally limited when it was released, I don't know. To me TS4 doesn't really feel like an improvement over TS3 - it seems more like a sideways move with equal parts exciting, new features and disappointing lack of other features. I'm not sorry I bought it, but I don't love it, or at least not yet.
LIKES
New CAS - it took some getting used to but I love how my sims look even more than I did in TS3.
New build mode - I love being able to place whole rooms. I can't tell you how much TS3 time I spent ripping stuff down and redoing it. Hopefully the upgrades to build mode will reduce this.
New collectibles, skills and professions. Lots of stuff to do! Treasure maps!!!
Aspiration and Wishes - similar to TS3 in concept with some variety so that it doesn't feel like a rehash of TS3.
Emotions
Achievements - you can unlock items for completing achievements. I got a 'romance' item for having a gold-medal date. I don't know yet if the item is unlocked across all games or just for the sim who completed the achievement.
Social Goals - There were specific activities that my sim was tasked with on her first date. The more she completed the higher level she finished with (in this case she finished a gold date) and the better the reward. This is linked in with the achievements.
It seems easier to discern other sims' traits.
Multi-tasking
Separate friendship and romance relationship meters
2 towns and easy travel between them
DISLIKES
Not enough customization options in CAS and build mode - I miss being able to apply custom patterns to my sims clothing and furnishings. I know it is possible to do custom recolors but the process is so cumbersome and involves at least one 3rd party mod that I won't bother with it.
The furnishings, build items, and clothing options are pretty limited, but I assume EA is already working on SPs and store items to fix that.
The controls are different enough from TS3 that I find them not particularly intuitive and I am having some trouble adjusting. However, I think this will be less of an issue the more I play the game.
No moodlet manager!!! It appears to have been replaced by a potion that clears negative moodlets. I presume this is a single use item and we will have to buy a lot of them if we want to get rid of pesky moodlets.
Game is laggy on my PC, which is pretty robust - although the graphics card could stand to be updated. Loading screens between neighborhoods take at least a minute, sometimes more.
Sparse information on items and collectibles. For example, I can send off my crystals, gems, and metals to the geological society for$20 and they will send back elements. I can put the elements in a display rack and study them, increasing focus, but I haven't found any other use for them besides selling.
It seems harder to build relationships with other sims. I assume this could be easier by taking advantage of emotions and objects with emotion auras.
No consignment store or self-employment - I assume this will come back via an EP somewhere down the road.
Towns and neighborhoods seem very small.