I believe you do. And, it would be wise to do a full install. If you go to the App Store under "Featured", look under OS X Utilities, which is below the window with the Yosemite Upgrade, and you will find it; but, be aware that it is an extremely lengthy process although it is well worth the wait. You can, of course, simply upgrade if that is all you want to do, but a full install is better.
I simply updated from PB6 and the release version installed in a snap. Not sure if it's worth the big download though, PB6 is perfectly fine. I'd wait until the first incremental updates start rolling in before updating, doesn't seem to be much of a point to it at the moment.