[tor-relays] What to change for v0.2.5.x?

So now Tor v0.2.5.x Release Candidates are available. Can someone give an overview of what's new for those who don't follow the development process?

What can/or should be changed in a working v0.2.4.x relay config to accommodate the changes made in the new code?

Are there particular areas (IPv6, multi-threading, etc.) that one should be aware of when moving from v0.2.4 to v0.2.5?

The changelogs do a great job of describing the changes between point releases but are somewhat overwhelming when attempting to determine the differences between major releases. If would be great if someone could give a brief(-ish) description of those changes.

Thanks.