one is our first non-beta-branch update to Bionic Dues since it released, and so it comes with a plethora of goodies from 1.001 on upwards in the release notes linked above.
The biggest thing, by far, are the improvements to the customization interface. The game supports a minimum resolution of 1024x720, and so our previous customization interface basically adhered to that at the expense of using the screen space of larger resolutions. Now on resolutions that are 1280x768 or higher, you get a new and easier-to-use customization interface that combines a number of functions into one screen. If you prefer the old interface for some reason, there is a settings option that lets you re-enable that.
A number of balance improvements are also in this version. Sentry turrets are no longer OP. Groups of ClawBots are no longer death on wheels. Tuck now has an improved special ability. And the pistol has been buffed quite a bit. Among other things.
This is a standard update that Steam will automatically download for you. However, if you want to force a quicker update and are currently running Steam, just restart Steam.