Cluny is notable because it begins a history of reform in the church that stretches through the medieval period. These reforms are sometimes aimed at correcting the laxness in the life of the monks, and sometimes are aimed at re-invigorating spiritual life. The second aim means that more immediate forms of spirituality (particularly mysticism) often find a home in these reformed church structures.
At the same time, Cluny ushered in a cultural renaissance to the church. Churches were more ornate. The person mostly responsible for these reforms was St. Odo (878-942), and they were mostly associated with the Abbey of Cluny in Burgundy.
Bernard of Clairvaux was a strident critic of the Cluniac reforms. His Cistercian reforms, 200 years later, were more austere.