So I've had a few hours with this, and I've compiled a list of my likes/dislikes compared to Sims 3. I'm not going to cover toddlers/pools/basements since everyone knows about those anyway.
The Bad.1) No "grab leftovers" interaction on the fridge. You want the leftovers in there? You have to click open, then click on the food and select "take serving"
2) "Chat with someone" from the computer BARELY fills your social need. You basically have to do it all day if the social need is yellow. It also doesn't add them to your relationship panel, so it's as if you never met them.
Oh... and it doesn't increase fun.
3) Calling someone lasts for a minute... max. You need to call them about 6 times to get any kind of social boost.
4) The "worlds" have about 10 houses and 5 community lots. That's it. Supposedly there are 1 or 2 secret lots you can unlock.
5) There doesn't seem to be a "Work Out" function on the TV anymore. You either need gym equipment or to go jogging. If you are energized, you can do sit up's and push up's, but they don't seem to increase athletics... just fulfill whims.
6) The fire alarm going off does NOT summon the fire brigade... so either put the fire out yourself or watch the house burn down if you haven't installed a fire prevention system. In fact, there's no fire or police service from what I've seen, but there's also no burglars either.
7) The camera controls are awful. At least you can set it to "Sims 3 mode", which fixes that.
8 ) Bit too cartoony on the art style for my tastes.
9) The action queue is limited to 6. Sims 3 had 8, and people thought THAT wasn't enough.
10) You can walk past your neighbors houses, but visiting them requires a loading screen. Oh, and there's no way to tell if a house actually has people in it or not WITHOUT visiting! You can tell if it's actually owned or not though.
11) Pathfinding is still a bit of an issue. I've had a sim standing in the middle of the floor, with nothing around her, and yet my sim cannot go and talk to her because something is in the way. What is in the way, Steven? A speck of dust???
The Good.1) Loading times. Instead of taking nearly 10 minutes to load from clicking the icon on the desktop, then into my saved game (this is Sims 3 + SP's and EP's is on a 5400rpm laptop hard drive. It was about 6 minutes with base game), it's more like 1 minute... maybe 2 at most. That's pretty impressive!
2) The emotion system. I love all the extra interactions based on what emotional state your sim currently has.
3) Career's. Okay, we don't get as many... that's fair enough. But I love the fact you have to do very specific things in order to be promoted. It's not just "level x skills as fast as possible, go to work in a good mood and have loads of friends." I have a criminal right now, and she's got to pickpocket 5 people and have mischief level 4 to be promoted (I think she's currently level 4 in her career).
4) The aspiration system. I love the fact you can change it and keep your progress.
5) Smoother animation. I don't think this is a product of the performance increase. It looks like Maxis have REALLY paid attention to animation in Sims 4 vs Sims 3... and it is glorious.
6) The programming skill. Just... the programming skill!
At this point, I feel as if the game is more like a sequel to Sims 2 rather than Sims 4. In fact, they probably could have called it The Sims 2 HD and that'd be a somewhat accurate description of the game. I do like Sims 4, but I feel it's just missing too much. Aside from Fun and Social being absolutely horrible to keep balanced (since being social no longer grants Fun, or it didn't for me), I find the game a lot easier to play. When I just want to vegetate and chill out, I can see Sims 4 being my go-to game.
When I want a deeper experience, I'll be loading up Sims 3.