Notice in the upper right corner (circled in red) it says "Older Version". When I first logged into Gmail it said, "Newer Version". I clicked it and nothing noticeable happened except I noticed the URL changed from this:
To this:
So far the only change I've noticed is in the Contacts and it appears that it's being rolled out gradually as it's only in one of my accounts and none of the people I've chatted with have it yet.
I wrote the Google Person inquiring about it. Google Person wrote back promptly (MAN! They work some crazy hours!) and referred me to the Official Gmail Blog. While it doesn't mention a new UI specifically, it looks like they're going to be gradually releasing new changes. Keep your eyes peeled!
Digg this story here.
