The problem that I've found with those environments is that the 60% of downtime you have is usually when people are socializing instead of working. That means i

The problem that I've found with those environments is that the 60% of downtime you have is usually when people are socializing instead of working. That means it's not actually that easy to focus on your own project. Also the office laziness rubs off and you tend to be less disciplined to work on that personal project than you think you will be. Perhaps somebody out there can consistently pull it off, but I've never seen it.