I love my Google Voice service and my Google number. It is what I give out to many people now. If I decide to switch between carriers everyday (I have multiple carriers to test phones), I can just change which one it forwards to my current primary phone with worrying about number portability. I also have that number set to forward and ring both my desk phone and cell phone during the working hours during the work week. So, I am probably one of the few people not tempted to take advantage the new feature that lets you use...

Google Voice with your existing number

If you check Google's...

Basics: Using a Google number vs. a non-Google number

...you'll find quite a few features disappear if you decide to use your non-Google number with Google Voice.

I think I'm going to setup a second Google Voice account to test this non-Google number service. I don't want to mess around with my current configuration. "If it ain't broke, don't fix it" is my philosophy in this particular matter.