Honestly, Seasons is pretty much what I expected - seasons with limited seasons-related activities. My expectations were pretty low in the first place, and they did add extra features from older Sims games, I just wish I actually cared for them (I still don't see a point in the thermostat, and as much as a calendar would make it easier to see exactly when a Sim's birthday is (assuming that they will actually grow up on their birthday for once), it's hardly a necessary addition to me.
Holidays are nice, but I just don't have the patience to spend 30 minutes decorating for a 5 minute party (and most of my Sims hardly need to eat anymore, so I guess they'll just get fat). Kinda wish there was a 'decorate the house' button, now that's a feature I would find useful.