Rev 9.0 of the HII package was published in December 2008. Since then, a number of the tools have been updated for a number of reasons - bug fixes, enhancements, clarifications... Rev 9.1 consolidates all of these updates.
The most important change is perhaps HalConfig. As explained in two earlier articles in this blog, the "classic" process of achieving HAL independence, based on downgrading the HAL to a "lowest common denominator", has effectively broken down with the advent of the intel Montevina chipset.
Other changes include a progress bar in CopyDrivers, wildcard matching in CopyDrivers and more consistent logging.