I started working with Azure Security Center in July 2015 when it was still only available for some private preview customers. In December 2nd 2015 we officially announced that Security Center was available. The amount of changes since day 1 were absolutely incredible, and Security Center continues to evolve to address new threats, and new customer's scenarios. Many capabilities that are now available in Security Center were result of a direct feedback from customers, and you can still vocalize your concerns, suggestions, and feedback. Make sure to visit Azure Security Center Feedback Forum, and let us know how can we improve Azure Security Center.
For more information about Azure Security Center, visit our documentation page, and if you want to ramp up on Azure Security Center, make sure to take this two hours training that talks about Azure Security Center from ground up.