I didn't want to start a new thread, because this one already existed.
For me, Seasons has given me more bugs then I have ever had previously, and it's not just things relating to the extra gameplay or the seasons themselves. I don't have any custom content, but my sims keep getting stuck between levels of a house, being told it's worktime when it's really a day off, and getting random days off, even when it's not a holiday or they've had a family event. When I try to sell my inventory items when the game is paused, a spare item pops up in the actual game. I can sell it, and it goes away when I press play, but I've never had that happen before.
This isn't to say that everyone has these problems, though. This is just me and my slow computer. Everyone's experience will be different.
One thing it has fixed, however, is the wedding presents - I'm receiving those again