This isn't about the code, I haven't started testing it yet, but rather about the main description on the plugin page. It should probably explain the scope and features of the plugin itself, rather than just describing what and why Flattr is. Currently you have to install the plugin just to find out what kind of features it has.
Ideally the description should give a sense of what would be involved in a pluginless Flattr setup versus what the plugin will do automatically for us. As an admin of a major site, I would also like the description to give a sense of how it tries to maintain a small resource footprint on the site.
Thanks for the plugin which you've clearly put a LOT of effort into (based on the changelog, which is the best source of info about what the plugin actually does at this point ;)