Ask HN: How many Dynos does your Heroku app use?

I host all of my Rails apps on Heroku, and they all perform well on 1 Dyno. I'm curious to know what some of you have found to be the needed number of Dynos for your apps - many of which I'm sure are more intensive than mine.

If you can, some details about your Dyno usage and app load would be interesting to know too.