Just having weather in the game was enough for me to buy it. Definitely not going to get it from any other expansion what this has offered up. More of a game changer and really changes the atmosphere of the over all game and it's not just eternal spring in the game. Adds an element to that things don't feel predictable when weather can effect just about everything. Objects, your sims, their pets, and whatever your Sim might be doing that day.
Holidays with your sims feel pretty fulfilling compared to before. Feels like you're bonding with your family and friends and makin' memories.
While playing I just like to look around at the rain in tab mode or the snow. Kinda almost puts me to sleep because of how nice and peaceful it is.
Lot of silly things in it too to enjoy and lot of things added for every playable life stage to enjoy, so none of your sims don't feel left out at all. Especially coming down to the calendar. There's even surprise holidays you can enjoy too. My sims went out on a date and didn't have to pay for food or anything because of it. Good thing too she was flat broke.