The director of marketing at my company just got out of a meeting with reddit and is super hyped at funneling all our Facebook and Twitter dollars into reddit instead. I didn't have the heart to tell him he's five years too late.
I scoped out reddit as a marketer for a few companies over the years. It's just a standard brand awareness piece. Unless their targeting has got better, I recall you had to dump a minimum of $10k/month and your ad just "got shown" to whomever
I assume they let you target by subreddit and user interest now, but it still can't be that accurate