In mission control centers, a major part of the ground segment is the front-end and backend software which is used to assist payload and system operators in their daily tasks. YAMCS (which stands for "Yet Another Mission Control System" and is pronounced as yams, the sweet potato) is a software package which has been created for long-term payload operations. YAMCS is currently implemented at two User Support and Operations Centres (USOCs) as an extension to ESA's standard Mission Control System (MCS) for Columbus. This lightweight YAMCS integrates into the existing USOC architecture, fulfilling specific mission related needs that the standard MCS is not capable of. During the last three years, YAMCS has quickly grown and it has been tested in several conditions supporting multiple parallel commanding/monitoring chains. It provides secure access to telemetry/telecommanding by remote users, and it supports the operators in archiving tasks. This paper outlines why YAMCS is optimally suited as a solution when designing a "modern Mission Control System" and it describes YAMCS' strengths as middleware, archiving, and display technology. In May 2011, Space Applications Services has released YAMCS in conjunction with AISB/BIRA as open source software.