>My impression, more from the side lines, being a technical person occasionally involved in sales, is that it help in lead generation, but that the conversion ratio tends to be lower than with leads for a closed product.

This is what I'm seeing. Even when I had free trials, vast majority of people were just free loaders, some even going as far as using a prepaid card to get past the requirement.

Which is why I'm hesitant to jump on the Open source wagon, I don't want an army of freeloaders now demanding and whining, like I see all the time on github.