I’ve been using this since shortly after its introduction, and could not be happier. It gives the "cut, copy paste" balloon that iOS uses for selected text, but then adds extensions: as a scholar I use a translation extension constantly, along with various linking tools- google, wikipedia, etc. I still can’t believe Apple hasn’t bought this up and incorporated it into the OS (where it belongs). In interface terms, the next best thing to sliced bread.
Panegyrist about PopClip