Once considered a "poor man's drink" in the areas of South America where they did not grow sugarcane, and a favorite of Hemingway - probably because it was cheap. It had a brief flare of popularity in California during the Gold Rush as passing ships loaded up on it and took it to San Francisco as it was actually cheaper to ship Pisco from Peru and the ocean voyage north than to ship whiskey overland. After that period, it became a curiosity in North America and rarely found.
There were a few abortive attempts (and brands) in the 60's and 70' s when I started to drink it but it was very hard to find and the quality was really not there (in retrospect). It is now enjoying a renaissance in cocktail circles as a versatile and interesting spirit and as such we are seeing a plethora of brands entering the fray.
Like any other spirit (absinthe in particular springs to mind) there are some major differences in process, type, and quality depending on whether it is made in one country or another - in this case Chile or Peru, and even whether ones area's spirit can be called the same name (much like the Czech vs. French and Swiss Absinthe debates).
The rapes are from a single estate and use the Quebranta and Italia grape varieties (exact porporation is proprietary). Distillation in Peru is carried out in alembic type copper stills (in Chile they use Column Stills) and by law they are barred from adding water to bring a distillation down to proof so again they have a much more flavorful yield - the higher the proof you distill the less taste you - have making this pisco very flavorful. The distillate is placed in flavor neutral tanks to age and mellow without the intrusion of wood influences which could compromise the flavor.