Cloud computing technology has reached a good level of maturity. The market of cloud resources is still dominated by proprietary solutions for what concerns resource delivering, pricing models and service level agreement. The research community is working hard to define specifications that try to standardize most of these aspects. When standards will get mature, customers will no more be locked-up to any proprietary technology, and full interoperability among clouds will be a reality. In the future cloud resource market the competition challenge will be played on the real capability of providers to accommodate customers' requests in a flexible way and to supply high and differentiated QoS levels.