I am currently using The Hit List (used OmniFocus, but then moved to Things, and then to THL).
However, I will be getting an iPhone soon and as THL does not as of yet have an iPhone app, I wanted to move back to OF (as Things does not quite work like I want it to).
THL does not export stuff, but it does support AppleScript, so I wrote a small script that creates new tasks in the OmniFocus Inbox using the current selected tasks in THL. Here is the script just in case somebody else needs to move.
You still have to do manual work, but not as much as you would have to. It would be possible to create a script that traverses the folder and list structure of THL and replicates it in OmniFocus, but this is Good Enough™ for me.
Code:
tell application "The Hit List"
activate
set tasklist to selection
set singleTask to true
if tasklist is not {} then
repeat with theTask in tasklist
set theStart to missing value
set theDue to missing value
set theOmniTask to missing value
set theTitle to the title of theTask
set theNotes to the notes of theTask
set theStart to the start date of theTask
set theDue to the due date of theTask
tell application "OmniFocus"
tell default document
set newTaskProps to {name:theTitle}
if theStart is not missing value then set newTaskProps to newTaskProps & {start date:theStart}
if theDue is not missing value then set newTaskProps to newTaskProps & {due date:theDue}
if theNotes is not missing value then set newTaskProps to newTaskProps & {note:theNotes}
set newTask to make new inbox task with properties newTaskProps
end tell
end tell
end repeat
end if
end tell