Rendering is now updated to include 1.7.2 blocks. The new Dark Oak and Acacia stairs are still not rendering properly but I'll have a look at those sometime over the weekend and get them working. If you were using the 1.6.2 render engine your world is automatically moved to the 1.7.2 render engine. If you have a specific reason to switch back to 1.6, edit your world and select the appropriate engine to render your world.
On an unrelated note,
Ethos has succeeded in crashing the server on Halloween night by releasing his new world. You can
download it here. Don't forget to visit his
Youtube Channel and subscribe!
I have an upgrade coming which should prevent this from happening. Or at the very least it will take a little longer to blow up when Ethos releases his wrath of subscribers on our servers.