I've noticed a *new* (correct me if i'm wrong) feature on Gmail.
When you hover an unread email, the line will turn green, and when it's already been read, the line will turn yellow.
I checked for my labs settings, and no feature has been added nor changed.

Unread email:

img329.imageshack.us/img329/35 ...

img329.imageshack.us/img329/49 ...

I'm not seeing it

not seeing this.. I'm on lab too....tis seems to be nice feature /visual effects..but dont we already know what read/non read items in gmail. ITs alreadly Bold/not bold correct ? so why the clutter ?

That's a Greasemonkey userscript. I have it via Lifehacker's Better Gmail extension. It's *not* a Gmail core feature.