After A Breakout 2011, Yammer Is Working On A Big New Funding Round
We've been using Yammer for the last couple years, so I have some perspective here. (And time for a disclaimer: all opinions stated are my own. I don't speak on behalf of my employer.)
Yammer's kind of a good news - bad news scenario. On the one hand, the basic functionality is great, and it really scratches an itch for organizations that have grown past the point where you can keep track of your coworkers via face-to-face interaction. It's relatively easy to use, basically reliable, and adds a new way of communicating that can be very effective in breaking down siloes.
On the other hand, Yammer can really break down when you start asking it to perform more grown-up tasks. To cite one example, how about analytics: a set of charts and graphs that show usage? Yammer doesn't really have that; there are some built-in statistics, but certain core stats (for instance, most-followed users) aren't included, you can't export data in Excel or CSV format, etc. The Yammer guys know that their customers need this (badly -- try to demonstrate R.O.I. without data) and they're "working on it" but there's no timetable for improvements. Likewise with the mobile products, which are sometimes great and sometimes a little buggy. I love the product and have advocated for it strenuously, but I've also spent more time than I'd have liked explaining Yammer's limitations to my colleagues.
My sense in dealing with the guys at the company is that they're young, smart, enthusiastic, and maybe a little overwhelmed. Hopefully they'll take this money and apply it to beefing up personnel and building out the product where it's still weak. (The linked article suggests the money might go instead into marketing and international expansion, which isn't going to solve anything.)
(Update: looks like I'm not the only one with reservations.)