tommig:

Is there anything new in 81.6 worth updating my source for? ( I've been very busy, and haven't played it yet! :/)

Which version was it before? The changes listed on the main page are: (I changed some descriptions)

Version 81.6
Fix zoom in decorations mode //Was broken in 81.5

Version 81.5
Allow Lua Key event function to override keys used by stickman and zoom
hanged Hide intro text when opened by PTSave link
Added Console button to quick menu

Version 81.4
Fixed issues with saving current menu (Walls is a valid menu)
Fixed crash when pasting long text strings
Disable decorations in save thumbnails

Version 81.3
Reduced lag created by PLNT
Optimisations to improve speed with GOL
Added more checks for invalid elements
Added brush size to Lua environment (tpt.brushx, tpt.brushy)
Added brush "Alt Selected" element to Lua environment (tpt.selecteda)
Added mouse wheel to mouse event arguments (mouseX, mouseY, mouseButton, mouseWheel)
SALT will only melt ICE if the ICE if above salt-water freezing temperature
Updated README and LICENSE files

There is no way to undo the change made in 81.4 though, theold thumbnails are already gone. None of these changes are really any interesting, so I guess it doesn't matter.