how good is Oly macro adapter w/40-150?

I have all of the following items and my ranking would be something like this:

1. Oly 60 mm macro lens (by far the best option)

2. Oly 12-50 mm kit lens in macro mode

3. Oly 40-150 mm with M-CON

4. Oly 14-42 mm with M-CON

IMO if you have the 12-50 kit lens it is not worth it to invest in the M-CON because the results are not so good (some fringing is quite visible). If you want to take macro photography more seriously than you have to save up some money and get the Oly 60 mm macro lens (alternatively Pana 45 mm).