On devices with a 5-way d-pad, the default action for pressing the center button now checks off the highlighted item. There is a new "Hold center button to check item" option in the Misc tab of the Preferences screen (not all devices support press+hold). The change in behavior is needed because the Treo detection fix in v3.0 build 3930 led to HS finally realizing that several other devices also had 5-way d-pads, which in turn led to some unexpected quirks on certain devices.
The Details screen now supports hardware navigation mode on devices that have the hardware navigation feature (the blue aura that highlights the current control). Up/down still go to the previous/next item.
The Best Buy screen now shows the percentage difference and unit price difference between the two products.