What follows is a list of observed changes in each version of World of Goo since the initial release. 2D Boy haven't released an official changelog, so this may not be complete.
Most North American retail boxes contain version 1.00, and Steam is currently stuck at version 1.20. You can upgrade both to version 1.30 with this patch.
European boxes already contain version 1.30.
Initial launch version.
* You can now configure the refresh rate
* Mac support
* You can now launch levels from the command line (used by WOG Editor)
* Players can now get the OCD flag in MOM even after they've talked to her
* Widescreen fix: the "continue pull-lever" doesn't fall off the screen when you finish a level
* Updated Language files
There were no code changes in 1.30 (the exe is the same), so I suspect the following changes were actually in 1.20:
* Fixed some players running the game with a non-admin login did not have their progress saved
* Progress now saves properly on Czech and Swedish Windows versions
* Fixed some users got a black screen on launch with sound but no video
* Linux support
* Unicode characters are now stored correctly in the user's profile.
* 64-bit support