The RGS instrument is the X–ray spectrometer on board the XMM-Newton satellite, launched December 1999, and still fully operational. It consists of a reflection grating to disperse the incoming X–rays and a CCD camera as detector. In the past fifteen years a lot of experience has been gained in operating and calibrating this instrument. In this presentation we report on the calibration methods and status, new instrumental modes and detector performance, which were acquired and developed based on the in-flight experiences with the instrument. Selecting the proper operating modes, combined with careful data processing based on target characteristics and science goals, allows detection of weak spectral features, despite slowly degrading detectors due to radiation damage and contamination. At present the instrument has excellent health status and performance, and will be one of the few major instruments for X–ray spectroscopy in the coming years, until supplemented by new missions like ASTRO-H and, in particular, Athena.