The patch contains various bugfixes and game improvements such as widescreen support, and provides some GUI tweaks. It also enables the use of the FMSel fan mission loader frontend with Thief 3 and bundles the most important T3 mods. It works with the GOG and Steam versions of the game.
With the improved configurability of the Minimalist Project in 1.1.9, play styles are now optional. Disabling them will revert to the standard difficulty settings as seen here. The GUI back buttons can now be enabled too.