A Applescript to migrate all tasks out of Cultured Code's THings for OSX and put them in the proper text format for Taskpaper from Hog's Bay Software.

Things2Taskpaper

-- modified on  21 Feb 2013 by Daryl Manning
set thePath to (path to desktop as Unicode text) & "Things2Taskpaper.taskpaper"
set thingsToDoFile to (open for access file thePath with write permission)
set eof of thingsToDoFile to 0
set cr to ASCII character 10

tell application "Things"
  
	-- Export to-dos from Inbox
	write "Inbox:" & return to thingsToDoFile as «class utf8»
	repeat with td in to dos of list "Inbox"
		set tdName to the name of td
		set tdNotes to the notes of td
		set tdDueDate to the due date of td
		set tdCompletionDate to the completion date of td
		set tdTagNames to the tag names of td
		write tab & "- " & tdName to thingsToDoFile as «class utf8»
		if tdDueDate is not missing value then
			set tdGoodDueDate to my tpDate(tdDueDate)
			write " @due(" & tdGoodDueDate & ")" to thingsToDoFile as «class utf8»
		end if
		if tdCompletionDate is not missing value then
			set tdCompletionDate to my tpDate(tdCompletionDate)
			write " @done(" & tdCompletionDate & ")" to thingsToDoFile as «class utf8»
		end if
		if tdTagNames is not missing value then
			repeat with tdTag in (words of tdTagNames)
				write " @" & tdTag to thingsToDoFile as «class utf8»
			end repeat
		end if
		write return to thingsToDoFile as «class utf8»
		if tdNotes is not "" then
			set fixedNote to my replaceText(cr, "; ", tdNotes)
			write tab & tab & fixedNote & return to thingsToDoFile as «class utf8»
		end if
	end repeat
	write return to thingsToDoFile as «class utf8»
	
	write "Scheduled:" & return to thingsToDoFile as «class utf8»
	repeat with td in to dos of list "Scheduled"
		set tdName to the name of td
		set tdNotes to the notes of td
		set tdDueDate to the due date of td
		set tdCompletionDate to the completion date of td
		set tdTagNames to the tag names of td
		write tab & "- " & tdName to thingsToDoFile as «class utf8»
		if tdDueDate is not missing value then
			set tdGoodDueDate to my tpDate(tdDueDate)
			write " @due(" & tdGoodDueDate & ")" to thingsToDoFile as «class utf8»
		end if
		if tdCompletionDate is not missing value then
			set tdCompletionDate to my tpDate(tdCompletionDate)
			write " @done(" & tdCompletionDate & ")" to thingsToDoFile as «class utf8»
		end if
		if tdTagNames is not missing value then
			repeat with tdTag in (words of tdTagNames)
				write " @" & tdTag to thingsToDoFile as «class utf8»
			end repeat
		end if
		write return to thingsToDoFile as «class utf8»
		if tdNotes is not "" then
			set fixedNote to my replaceText(cr, "; ", tdNotes)
			write tab & tab & fixedNote & return to thingsToDoFile as «class utf8»
		end if
	end repeat
	write return to thingsToDoFile as «class utf8»
	
	-- Walk through projects, export as project with their to-dos
	repeat with pr in to dos of list "Projects"
		set prName to the name of pr
		set prNotes to the notes of pr
		set prDueDate to the due date of pr
		set prCompletionDate to the completion date of pr
		write prName & ":" & return to thingsToDoFile as «class utf8»
		if prDueDate is not missing value then
			set prGoodDueDate to my tpDate(prDueDate)
			write " @due(" & prGoodDueDate & ")" to thingsToDoFile as «class utf8»
		end if
		if prCompletionDate is not missing value then
			set prCompletionDate to my tpDate(prCompletionDate)
			write " @done(" & prCompletionDate & ")" to thingsToDoFile as «class utf8»
		end if
		write return to thingsToDoFile as «class utf8»
		if prNotes is not "" then
			set fixedNote to my replaceText(cr, "; ", prNotes)
			write tab & fixedNote & return to thingsToDoFile as «class utf8»
		end if
		
		repeat with td in to dos of project prName
			set tdName to the name of td
			set tdNotes to the notes of td
			set tdDueDate to the due date of td
			set tdCompletionDate to the completion date of td
			set tdTagNames to the tag names of td
			write tab & "- " & tdName to thingsToDoFile as «class utf8»
			if tdDueDate is not missing value then
				set tdGoodDueDate to my tpDate(tdDueDate)
				write " @due(" & tdGoodDueDate & ")" to thingsToDoFile as «class utf8»
			end if
			if tdCompletionDate is not missing value then
				set tdCompletionDate to my tpDate(tdCompletionDate)
				write " @done(" & tdCompletionDate & ")" to thingsToDoFile as «class utf8»
			end if
			if tdTagNames is not missing value then
				repeat with tdTag in (words of tdTagNames)
					write " @" & tdTag to thingsToDoFile as «class utf8»
				end repeat
			end if
			write return to thingsToDoFile as «class utf8»
			if tdNotes is not "" then
				set fixedNote to my replaceText(cr, "; ", tdNotes)
				write tab & tab & fixedNote & return to thingsToDoFile as «class utf8»
			end if
		end repeat
		write return to thingsToDoFile as «class utf8»
		
	end repeat
	
	-- Walk through areas, export as project with their to-dos
	repeat with ar in areas
		set arName to the name of ar
		write arName & ":" & return to thingsToDoFile as «class utf8»
		
		repeat with td in to dos of ar
			set tdName to the name of td
			set tdNotes to the notes of td
			set tdDueDate to the due date of td
			set tdCompletionDate to the completion date of td
			set tdTagNames to the tag names of td
			write tab & "- " & tdName to thingsToDoFile as «class utf8»
			if tdDueDate is not missing value then
				set tdGoodDueDate to my tpDate(tdDueDate)
				write " @due(" & tdGoodDueDate & ")" to thingsToDoFile as «class utf8»
			end if
			if tdCompletionDate is not missing value then
				set tdCompletionDate to my tpDate(tdCompletionDate)
				write " @done(" & tdCompletionDate & ")" to thingsToDoFile as «class utf8»
			end if
			if tdTagNames is not missing value then
				repeat with tdTag in (words of tdTagNames)
					write " @" & tdTag to thingsToDoFile as «class utf8»
				end repeat
			end if
			write return to thingsToDoFile as «class utf8»
			if tdNotes is not "" then
				set fixedNote to my replaceText(cr, "; ", tdNotes)
				write tab & tab & fixedNote & return to thingsToDoFile as «class utf8»
			end if
		end repeat
		write return to thingsToDoFile as «class utf8»
		
	end repeat
	
	
	-- Export to-dos from Someday
	write "Someday:" & return to thingsToDoFile as «class utf8»
	repeat with td in to dos of list "Someday"
		set tdName to the name of td
		set tdNotes to the notes of td
		set tdDueDate to the due date of td
		set tdCompletionDate to the completion date of td
		set tdTagNames to the tag names of td
		write tab & "- " & tdName to thingsToDoFile as «class utf8»
		if tdDueDate is not missing value then
			set tdGoodDueDate to my tpDate(tdDueDate)
			write " @due(" & tdGoodDueDate & ")" to thingsToDoFile as «class utf8»
		end if
		if tdCompletionDate is not missing value then
			set tdCompletionDate to my tpDate(tdCompletionDate)
			write " @done(" & tdCompletionDate & ")" to thingsToDoFile as «class utf8»
		end if
		if tdTagNames is not missing value then
			repeat with tdTag in (words of tdTagNames)
				write " @" & tdTag to thingsToDoFile as «class utf8»
			end repeat
		end if
		write return to thingsToDoFile as «class utf8»
		if tdNotes is not "" then
			set fixedNote to my replaceText(cr, "; ", tdNotes)
			write tab & tab & fixedNote & return to thingsToDoFile as «class utf8»
		end if
	end repeat
	write return to thingsToDoFile as «class utf8»
	
	close access thingsToDoFile
	
end tell

on replaceText(find, replace, someText)
	set prevTIDs to text item delimiters of AppleScript
	set text item delimiters of AppleScript to find
	set someText to text items of someText
	set text item delimiters of AppleScript to replace
	set someText to "" & someText
	set text item delimiters of AppleScript to prevTIDs
	return someText
end replaceText

on tpDate(mydate)
	set y to text -4 thru -1 of ("0000" & (year of mydate))
	set m to text -2 thru -1 of ("00" & ((month of mydate) as integer))
	set d to text -2 thru -1 of ("00" & (day of mydate))
	return y & "-" & m & "-" & d
end tpDate