Well, I have to say, I can hardly tell it's an EA sequel. As in, many little yet important aspects have changed and overall it feels different, even better, rather than a rehash like most EA sequels. It simply feels like they added details where they'd improve the gameplay and removed certain ones which neither made sense nor made the game more enjoyable.
Most of all, they slimmed down the amount of needs for a sim and made them far more managable. Environment is gone, your Sim will no longer go about whining all day over not enough pictures in the room, but there are mood bonuses for being in a well decorated room. You could say the mood bonuses/penalties sort of replaced the missing need bars (and they're used for near anything). Most of the others no longer take all day to fill up. More specifically, fun and social, which seemed to take forever in Sims 2.
They added little micromanagment details here and there. Most notably, sims now have an inventory and some objects are detailed (in a way) and physically there, rather than something that appears the moment your sim decides to take it from a shelf. For example, books. Your sim can now actually finish reading a book (afterwards he can re-read them, but they provide less entertainment), they've got variable amounts of pages and even genres (although what influence this has, I do not know). Unfortunately, this item-basedness appears to be limited to food, books, sheet music, insects and fish. I haven't seen video tapes or games like this, the TV and computer still works like a black void pulling resources out of nowhere. But the groundwork for expansion packs of this nature is there.
Speaking of expansion packs, the number one notable thing in the launcher is the new store. Here you can currently buy clothing and hair with real money. Not sure whether this means they're moving from the expansion pack model to the micro-transaction model, but it's there. Which makes me wonder how they'll limit modding to make it profitable for them. This also might be the reason why there are initially so few buyable items in-game.
Another detail is that you can now decide what your sim does at work, or how he does minor activities like exercises. For example, you may choose to have him slack off at work, or try to socialize with co-workers or suck up to the boss. And these influence his carreer, need bars and relationships. Also, the work places are now physically there, on the map. But you cannot see inside most places and "most" includes all the work places.
The wants are still there, but there's only 4 of them possible at a given time and they're selectable (as in, they pop-up in a small list and you may choose to promise this wish and add it to the 4 expected or decide not to pursue these wishes after all). There aren't any fears anymore, I'm not sure if they added anything in the Sims 2, though. Never stumbled upon a fear there myself. There's also the major aspiration, which you choose at the beginning of the game (among 5 selected by the game, based on the traits you selected), which, once achieved, gives 30k lifetime happiness points. Also, the rewards are no longer primarily items, they're mostly stat buffs now, like "steel bladder" or "multi-tasking".
The traits are a rather optional thing. You can choose 1-5 such traits, and there are positive as well as negative traits there, but there's nothing forcing you to balance this. You can take only positive ones for all you care, but perhaps they award you for negative ones later somehow. I wouldn't know, I took only positive ones.
A rather minor new thing is the opportunities. There can be three at any given time - work, skill or event related. The work related ones pop-up quite frequently and these range from doing some work at home on your in-game computer to coming to work after hours to fix something. Skill ones are quite similar, except they pop-up based on your skills, and people will ask you to grow something for them, repair something (being in the science carreer, my sim is a handyman-gardener) or simply talk to someone about something. The event related ones are things that pop-up in town regardless of your actions, like athletic try-outs or chess tournaments and you can freely choose to participate in them at any time. These can result in skill, carreer, relationship or financial bonuses.
The world is still tile-based, but these appear a bit less strict. That is, for every tile, there are 4 sub-tiles. So you can place a 1-tile object over 4 tiles, where each tile will hold a fourth of that item. Your sims still require a whole tile to get anywhere, though. I'm not sure if this was there in Sims 2, but they're also a wall-pull tool now. So if you'd like to expand a room without having to go through all the removing, adding and painting, you can just grab and pull it and it'll expand the room, even moving objects placed next to the wall along with it.
On the negative side, it feels lacking content-wise. As I've mentioned before, there seem to be few buyable items. Although that might be compared to Sims 2 + expansions. But the town also seems pretty small (there are pretty few activities available) and the collectible item types seem limited. Overall it just feels like a week-long game, after which you'll have probably seen most things it has to offer. I expect them to try to keep up the novelty factor by churning out micro-transaction content, though. And probably the next 10 or so expansion packs (although hopeful they'll keep the minor stuff like IKEA furniture to the micro-transactions).