Avantages
If you are not seriously tied to this company or its future, then you will occasionally enjoy free food, beverages (they've got a keg!), video games, a 9:30AM start to the work day, and a very chill atmosphere. There are few workplace policies, and those that exist are hardly ever enforced, so you can get away with taking time off, taking frequent breaks, or just enjoying time with co-workers.
Inconvénients
Other reviewers have already said a lot to define DZone's pitfalls. I'll only add that the biggest problem i saw was an unending commitment to vague expectations by the people who had built the company. The owners were constantly talking about where the company was going, but it only seemed like 3 or 4 employees had jobs that were well-defined enough to make any headway. The rest of us struggled to either create work for ourselves or do a different job each day as we were moved from office to office, fulfilling new roles each week or two.