The new user interface (with colorful backgrounds) is an example of one of the upgrades. You receive no notification on that.
Honestly, don't obsess yourself over your email account. Please, it can be very unhealthy. I still use the old Gmail interface (http://mail.google.com/mail/?ui=1) for the interest of optimization that the new user interface (ui=2) lacks.
I, for one, am NOT waiting in anticipation for Gmail to ever go out of
Beta. They might start charging for it then.
Maybe not, but you never know. I've seen some other nifty tools
change from Beta (free) to full product status (no longer free). I
don't mind staying a Beta-tester forever. I like finding problems and
giving them feedback.
Andy