The subscriptions are a great idea as it gets a whole variety of material out there for us to read. However, there's usually only a couple of stories in an edition that float my boat so value-wise it may not be ideal.
As an alternative how about a prepay service. For the sake of argument $2 gets you 1 download of your choice and you can prepay in any amount to use as and when you want. Possibly add a sliding scale so more up-front gets you extra downloads ?