Yesterday, a couple hours after my co-founder Mat posted on /r/entrepreneur, the post took off after 3 hours of not getting any traction (don't know why later).
Mat was super careful with not linking too much to be considered spam and noticed that the post became popular only after he woke up the next day, so we were slow to turn it into traffic.
Even so, 45 visits to our site directly from reddit (+ some probably through google) + a handful of new emails is a nice boost.
Further experimentation needed.