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...
A few more days into it and trying to adopt, I unfortunately feel the same way. If I needed to search for something very particular, I feel that I can now effectively do that from the mobile web interface. Whilst it "loads" on a mobile interface, it is near unusable from a collaboration, interaction, and participating perspective IMO.
Plus I get signed out all the freakin time, so I can't just pop on and post and be on my way.