I don't need another dyno. I'm already running way more than this app requires. (with addons, etc..) I think the service would be more fair if the time threshold for being set to idle was governed by the amount you are paying.
Yes, you are paying for a bunch of other services; but, well, those services aren't the actual web dyno that processes the actual request.
Perhaps they could phrase their offerings better, but my impression was that the 1 free dyno with idling is intended for development and testing, not for production use. Once you actually need to use it in production, you need to pay for a dyno.
So now I have 3 dynos (2 production, one staging) for $35/month, I can scale up or down at will, deployment is dirt simple, and I don't have to do the sysadmin crap myself.
It's an extreme bargain, IMO.
Now if the project takes off to the point where I need dozens of dynos all the time, that will be different, but ideally in that case I could hire a sysadmin. :-)