The disadvantage point of social integration in WP8 was it hard to update feature. You have to update your OS every times you want to add some feature. Not only that, if you create newly social network app. You have to wait for Microsoft to add them to OS. But in WP8.1 most of OS integrate feature become extension-like (e.g. Music, Video, Games, IM, Social Network). It easy to add a feature by update an app. You can integrate your social network app using API they gave us. Windows Phone 8.1 is now more flexible than Windows Phone 8.0. As you can see, now we can see sticker in Facebook comment, like a comment on Facebook even we see a post using People Hub (That we cannot do when we stuck on WP8).
The old way to connect IM was not flexible at all. You can't send sticker or voice or video. You can't even chat in group. And you can only use it with WLM and Facebook! Maybe it not a good idea to keep it.
For those "resuming" thing. It happen because your device come with 512 MB of RAM. If your device come with 1 or 2 GB of RAM it far better. Even my old Lumia 920 was hardly to see those resuming screen. (It look like 512 MB and 1 GB devices was double on memory. But the thing is the free memory space of them is about 4-6 times difference)