Right now there's a bit of a sewage spillage problem, as well as phantom pollution clouds coming from nowhere. The good news is that traffic has improved and firefighters do their job. Hurray!
Sadly it's the new glitches and bugs that have hitched a ride with update 2.0 that's putting a serious downer on all the fun. Overall though it has been a boon for the game.
Right now air pollution is a major buzz kill as it appears out of, well, thin air. You can have your city blanketed in thick smog clouds despite there being no other city in the region, which causes major health trouble. Sewage can also spill over at buildings despite having excellent treatment capacity - my ferry terminal fell prey to this literally crappy bug.
Firetrucks are improved 10 billion percent as fire coverage in a city is now working as intended/logic dictates. Traffic flow has improved as have mass transit systems but that isn't to say we're out of the woods when it comes to odd behaviour. Despite the promise to fix audio issues with update 2.0, some are still having very strange issues with regards to sound.
Maxis have acknowledged the air pollution bug and are working on it, so hopefully a hot fix soon.