NewsBlur (social feed reader) uses Redis pubsub for real-time as well: http://blog.newsblur.com/post/20371256202/building-real-time.... Now I'll have up to 500 concurrent clients, but I couldn't be happier with how utterly simple it was to get Python to talk to Redis to talk to Node to talk to Socket.IO in JavaScript on the browser.

I use it during feed fetching to notify all of the users subscribed to a feed's updates.