Let's see if I could answer this one.

1) contacts are pulled down automatically (and you can merge them with existing contacts)
2) Chats do combine between you and one contact (sms, various messengers)
3) converstations shows a list of activities, if you choose one of them, it opens up the combined conversation between you and that particular contact

All in all, very much integrated and easy to use and always online.

I especially like the way you can add a contact as a shortcut on the desktop. It names the picture after a nickname (if you have it specified) and if the contact has defined IM etc, it shows a notification icon when your friend is online.....great stuff.