I miss the Sidekick.
The article's right, but the picture caption's wrong - Microsoft didn't make the Sidekick. The Sidekick was made by Danger, who Microsoft later bought.
Frankly, the Sidekick was the best messaging phone I ever used. The IM clients were very tightly integrated into the OS, as was the Twitter client. I don't recall if it did Facebook or not. (I think there was an app for it, but since the appstore is gone, I can't fire up my old one and check.)
The SSH client was rock solid (critically important for me), the keyboard was excellent, and the web browser was one of the better mobile ones at the time. The apps were pretty weak - some games, calendars, and so on - but it was more of a mobile terminal than a smartphone.
I wish I could get a phone that handled messaging as well now. My Blackberry comes close, and could match it if someone wrote a good BB10 Hub-integrated multi-IM client.