Flattr strangely seems to have taken off in Germany fairly quickly. And it seems to work. If you are a popular blog you already (with Flattr still being invite only until very recently) seem to be able to make between a few hundred and maybe a thousand Euro per month.
Another area where it may be taking off is Free and Open Source Software. See http://raphaelhertzog.com/flattr-foss/ ; dpkg is currently in the top 5 most flattrd things.
