Dadspeed is the most popular server on Eco. Its a long term server that lasts for months. What sets it apart of the super skill system. You can't have more than 2 skills and they can't work together. Like you can be miner and hunter but not miner and smelter. Dadspeed is named because you can play as much or as little as you want and still be relevant. You can join months into the season and find a place.
Dadspeed is a great server and offers a truly unique experience, but I wouldn't call it the most popular server - the severe restrictions on the skill system is something the vast majority of our audience actually doesn't like. It certainly is one of my immediate candidates for the upcoming recommended server list, though, and I have been recommending them personally on several occasions.
We do hope that our improvements to the exhaustion system will allow servers that offer a similar experience without being as limited in the future, which can cater more towards players that have limited time available to play, but don't want to be limited to a very small selection of skills. We'll see soon enough, Update 10.2 is going into playtest soon.