We use it on a daily basis. It's... well, let's say its better than any of its competitors. We tried using Salesforce Chatter, as well as Jabber-based solutions

We use it on a daily basis. It's... well, let's say its better than any of its competitors. We tried using Salesforce Chatter, as well as Jabber-based solutions, none worked as well as Yammer does. Still, Yammer has plenty of problems. Their iPhone/iPad apps suck badly (as an example, getting rid of a notification requires 3-4 actions within the app), but at least they exist. Their desktop app is Adobe AIR based, which means all kinds of bloat, slowness, annoyances and bugs. Let's put it this way: if I could get Yammer with a mobile interface like Tweetbot or at least Twitter, I'd be happy.