I just upgraded my blog from WordPress 2.6.1 to WordPress 2.7. Whew it was hairy and took 1.6 hours to do, but I have successfully upgraded my blog platform.
You the user can most likely see no difference, but in the control panel, the differences are huge. For me the reason that I wanted to upgrade was (1) so many clients are asking me should they upgrade? and (2) Flash Player 10 has broken my ability to easily add photos to my blog and I wanted to see if upgrading would help to get me back in business.
Well I am here to say that yes for images I am back in business, thank goodness. Darn that Flash Player 10 for making it so hard for me with WordPress.
So do I like the interface of WordPress 2.7? Well, it is very different than 2.6 that is for sure.
So far for me all my plugins have worked and my settings have carried over. Do I recommend doing the upgrade? If you have the time and money, I would recommend it. One of the improvements I see is the ability to block specific users from commenting, I have one guy who spams me all the time, and the ability to from now on auto upgrade WordPress as new versions come out. I liked WordPress version 2.6 but I think that I will like version 2.7 better.