From the Tiki home page:
Plenty of good news; install script added, notable performance improvement, less memory consumption, and alot of new features! This version also fixes several bugs found in Tiki 1.5 and 1.6RC1 users that want to enjoy the new features are encouraged to upgrade.
You should be able to check out the latest version at the tiki test site. This project has come a long way since I first stumbled upon it. Congrats to the Tiki team!