The way the left side bar is handled is similar to the new Gmail theme, "Preview". Whichever category you are in is highlighted. Quite a subtle change overall actually, but I like it. I must admit though, I’m not a big fan of the yellow color the box changes when you select it via the check box near the contact picture. It seems that Google is trying to roll out similar feel across all their web apps. Looks good so far.
Written by: Andy G.