I'm making progress on the Fiona manual: https://github.com/Toblerity/Fiona/blob/master/docs/manual.rst. When it's finished, there will be a Fiona 1.0 release. If this doesn't help you understand when and where you'd want to use Fiona over OGR's own Python bindings, let me know. Also let me know if you think I'm misrepresenting those bindings. I'm a big fan of GDAL and OGR, but I don't want to tip toe around its gotchas. I want to banish them.