From personal experience -- switching from socket.io to socketcluster.io for our conferencing platform was a life saver. Its so much more stable & performant its crazy. We also use it to run our webrtc video chat platform which works great as well. Cant say enough good things about this.
Should say that we horizontally scale this thing pretty heavily using the sc-redis module. Elasticache + ELB + 4 EC2 Instances = support for 5000+ person conferences :D
What are your montly costs?