Upgrading from 9.0-STABLE to 9.1-RELEASE with freebsd-update?

[Joshua Isom]

I've used STABLE for years, but with csup going away, I don't want to 
deal with adding extra packages, and keeping them unbroken, just to stay 
up date.  Running freebsd-update doesn't work for people running STABLE, 
and I'm not sure freebsd-update will work properly anyway if I compile 
world for myself.  What's the best way to switch from running STABLE to 
running the RELEASE channel?