Apple Employs some where in the region of 3500 to 4000 people in Ireland. They have a massively skilled workforce and manufacturing plants that provide for all of Europe there. A lot of large multinational companies locate there due to easy access to skilled English speaking workforce and easy transport to Europe and beyond. Just the other day I was in a Sydney data center and saw an EMC unit being delivered from Ireland. Remember up until the past year people in Ireland had no fees for third level education so a large % have degrees, many in IT related fields. The low tax for technology companies is a bonus but not the sole reason they are there.