We've waited for this so long, actually, since The Sims was released. Seasons is another great expansion pack, with lots of new features, including the seasons (duh), awesome weather effects (snow, lighting) and new family-activities like new pool games, building snowmen, skating and many more. Also, your sims can now grow plants, trees and vegetables (and juice, sell or cook them!), and if you're good in it, you will turn into new type of sim. If you have TS2, buy this. You'll love it. And your family will love it.
Shortly, Seasons is easy to learn and play. Friggen addictive game!