Unfortunately the price model puts it in a place where it is the right technology only for some very rare places.
In a nutshell the key thing you need to know is: - The storage is 6.4x expensive than classic S3. - The GET requests are 2x cheaper (with additional cost for large requests). - Your data is replicated within a single region. - latency is single digit ms.
From a pure cost wise point of view, the realm where it makes sense to use it is there, but small, and often competes more with EBS than it competes with S3.