Great topic of discussion ...
If the draw is your content, solely, you're more likely to have higher conversions ... weeding out the freebie seekers, though you may not bring in as many subscribers overall (I think too much focus is put on numbers, anyway ..
).
If you promise a continuing stream of theme based instructional content, such as a tutorial series, etc., or a free download of the month (not necessarilly commission based, but high usability) you should hold the interest of those that are really, well ... interested.
I think establishing and nurturing self brand, trust, and credibility should be the main focus ... not the give aways.
But offering ONE thing, as an initial incentive, may be a good way to get the general masses to commit ...
After that, it's up to you to sell yourself, first ... then your wares.
Regards,
Mike "questions? ask your subs!" Merz