While the plugin correctly appends "http:" to the cover image source for FimFiction stories, it isn't doing so for the rest of the images in-line with the text anymore. This means that while the epub can be viewed without problems, converting it to any other format causes calibre to get stuck trying to find an invalid URL for every image (even though the images are cached in the epub).
Here's one story which has a significant number of in-story pictures that illustrates the problem:
http://www.fimfiction.net/story/1218...amlp-crossover
Also, I can only make edits
once to the epub generated by the plugin for the story linked above before I can't access file0001.xhtml within the epub. After making edits once to the epub and saving, further attempts to open that particular xhtml results in calibre-parallel.exe (and therefore the book editor) crashing. The remaining contents of the epub (including the other xhtml files) can be opened in the book editor without issue. This problem is not fixed by restarting calibre and the only solution seems to be deleting and re-downloading the story using the plugin.
I haven't tested to see if other stories have this editing issue so I don't know if this is a problem with calibre or with the plugin. I am using calibre 2.7.0 [64bit] for Windows, if that helps.