The wormwood/thujone content in properly made Absinthe is quite low. It's really all the other herbal extracts which have many compounds that are related to caffeine and ephedra.
The net effect is a lucid buzz, similar to a strong Irish Coffee, Cauppichino and Sambuca, or any of the energy drink + alcohol concoctions that are now popular in clubs. Plus a healthy dose of psychosomatic reactions based on Absinthe's reputation, and feeding off any company you were keeping who were also imbibing.
What actually got Absinthe banned here in the States were low-end unscrupulous makers using heavy metals, chemical dyes and methanol to try and mimic Absinthe's strong alcohol content and unique color, and the way it would change from clear to cloudy when dispensed into water.
That, and Absinthe's association with less-than-stable artist types and bohemians did it in legislatively.