A new 1.09 beta just came out (and will be automatically installed for you by the ZLauncher). Here are a few of the changes you'll find in this release:
Quite a few bug fixes and small improvements.
More ACS features including new functions and operators, as well as improved support of older ones.
Implementation of in-game voice chat. It's intended for team modes, as well as coop/survival. You need to define a "voice" key that you need to keep pressed while talking. The server must also have voice enabled in the first place though: you won't be able to talk otherwise. There are many options/commands pertaining to voice chat. You will find more info at this document.
Here is the complete change log.Download 1.09 Beta 25 here.