i have all the expacs, and i quite enjoy them. it really just depends on what you want out of your game.
get to work adds three new jobs where you can go to work with your sim and control what they do for a better day with better pay. or a really crappy day with barely any pay. get together has a fun group mechanic. cats and dogs is fun, but it doesn't include any of the small pets like sims 3 pets did, you have to buy "my first pet stuff" for those if you want them. cats and dogs also introduces the veterinarian retail business. unfortunately, it doesn't count as your sim having a job, so if your sim is ambitious, they will get an "unemployed" demote every once in a while. it's the same issue with get to work introducing retail business and the dine out gamepack seems to have the same mechanic, but with a restaurant. seasons is interesting, it added a few fun concepts like holidays and making your own holidays.
