Modern web UI is nice, but at the end of the day when it comes to mobile, apps are still king.
If the purpose of this is to replace the interaction we had on Yammer, a mobile app is a necessity...
Agreed David Leveille a mobile app is a must but Microsoft can only do with the platform permits and Lithium have been slow to provide an appropriate SDK making this difficult for now.
Lithium has made inroads with an Android SDK beta last year and an iOS SDK beta has just been released in the last month, so the signs are good, Microsoft will be able to use these in due course.