I hope that this is not your final answer though.
Luis said that the old enhancement code was not maintained anymore and I am fine with that. But only if by 'not maintained' we mean that it should work as it worked before 5.0. This is not the case in this particular example.

Otherwise you should really go the whole nine yards and remove the old enhancement method (IntrumentTask) and document that only the new enhancement code should be used. If not, people may migrate to 5.0 from earlier release and still keep the old enhancement code as it is available and it was working enough for them (like it did for us).