Note: this post has been sitting in the drafts queue for some reason. Better to publish it. :)
As of Tuesday, Aug 4, 2015 Funsize has been enabled on mozilla-central. From now on all Nightly builds builds will get updates for builds up to 4 days in the past (for yesterday, for the day before yesterday, etc). This should make people who don't run their nightlies every day happier.
Firefox Developer Edition partial updates will be enabled after 42.0 hits mozilla-aurora, but early adopters can use the aurora-funsize channel.
Partial updates as a part of builds and L10N repacks on nightly will be disabled as soon as Bug 1173459 is resolved.
As a bonus, you can take a look at the presentation I gave in Whistler during the work week.
If you see any issues, please report them to Bugzilla.