I would offer a limited trial of some kind—probably a few days, enough to get a taste of the service without giving away the whole thing. That way I can get an early idea if the idea is effective.
(My list, by the way, is also not not dev-related—which might help you branch out your offerings some.)
quick 2 Q's: What industry is your list for. & what price would be low enough to not need a 'free' trial?
It's a history/pop culture NL with a lot of pieces on vintage technology (located here if you want an idea: http://tedium.co). I think if the cost were closer to $10 a month, it'd be closer to impulse territory for me.
done & done. I'm also letting go of the Dev only niche since I've been getting a bunch of feedback from other niches.