Facebook and Twitter have already been integrated deeply into Windows Phone, and we found out during the developer preview that Skype would also get deep integration, which wasn't surprising given that Microsoft now owns Skype. But, for Windows Phone 8, Microsoft has updated the apps for all three services to better integrate with the OS, and have better overall performance.
We had seen before that the apps would all have notification access on the lockscreen, but there is more for Facebook and Skype. The Facebook app will allow users to access calendar events on the lockscreen, and have Facebook photos show on the lockscreen. Skype will be able to run fully in the background and receive messages and calls, and Microsoft claims that this will not drain the battery like a normal app running in the background.