There is a checkbox for "Premultipled Alpha" in the Input's Color Adjust tab. I am not sure what it does (not documented in the Help). Seems that when adding new Inputs the default state is unchecked. But, for Title Inputs it is checked.

Found this when I changed an Input from a Title to an Image with a semi-transparent png file. Could not understand why the Image was not transparent when I overlayed it. Until I finally found that Premultiplied Alpha was on.

Wonder if this is by design. In any case, some words about "Premultiplied Alpha" is most welcome :)

Thanks desmar (altough your link contains a "http" too much).
Still confused about the difference in the default setting when Inputs are added.
(and my brief browsing on the subjects suggest that perhaps Premultiplied Alpha typically is better).