It doesn't appear that the changes have been rolled out unilaterally. In at least one group in which I participate, the old interface is still what shows up. I don't know if that is something the group manager controls, but that's what I'm seeing.
While I like most of the changes, there are a couple of things I call into question.
Where happened to the 'News' tab?
One feature that is lacking in the new interface is the ability to submit news items which, in the old interface, were categorized separately from discussions.
Now, all submitted content except Jobs comes in the form of a discussion. The interface provides the ability to incorporate hyperlinks, which is great if it's a "news" item you want to share. The problem is, there is no way to distinguish what is and what isn't news.
There is already an abundant amount of self-promotional/self-serving content being passed off as discussions, and we don't need the platform itself contributing to the problem. That only makes the group manager's job that much more difficult. It would seem this change exacerbates the problem.
Will LIke, Follow and Comment change the nature of discussions?
Now that LinkedIn is behaving more like Facebook and Twitter in that it gives me the ability to "like" things and follow people, do you think that will change the nature of discussions? Will they become more casual, for example, and less business-like? Will we see posts about our pets or the restaurant we visited over the weekend? (I recently saw a person post a photo of their cat as their avatar.)
While I have no precedent to suggest such behavior will occur, as LinkedIn gets more like other, less business-oriented social networks, will it take on a more relaxed atmosphere? If it does, will that be a bad thing? Or, will a more casual attitude actually encourage its use?