The ACPI 4.0a specification has been released, with numerous errata, here. Most appear to be minor corrections and enhancements related to Thermal and Power-State Dependencies, and the error reporting data structures.
For all of you looking for more power & config excitement, ACPI 4.0 development has started with the usual cast of characters (Phoenix, HP, Intel, Microsoft and Toshiba). You can get a look at the draft specification, when available, by signing up today. See http://www.acpi.info/spec40.htm