I just barely upgraded all the sites to WordPress 2.7. The main advantage is that it will take you fewer clicks to do what you need to do. You will see that the menu bar, which was on top, is now down the left side.
Also, if there is an upgrade to something you are using on your site (a widget, a template), it will tell you and you can just click on the upgrade and do that yourself. It’s really easy.
We will have an online workshop on using WordPress 2.7 in Jan. Watch for it on our Workshops page.