I, too, have had nothing but problems with the Mail script working properly. A couple of emails have successfully sneaked through to become Actions in my Focus Inbox, but in a seemingly random fashion.

The Apple Console app sometimes shows this:

2008-01-21 10:19:44.683 OmniFocus[6373] .sdef warning for part of complex type 'color | text | file | point | real | integer | boolean | point | missing value' used in suite 'OmniStyle Scripting': 'missing value' is not a valid type name.