Superconducting qubits based on Josephson junctions and resonators are presently leading candidates for the implementation of quantum computing. These systems couple strongly to their environment, which often makes preservation of coherence challenging. This strong coupling can be turned into an advantage: it enables the investigation of noise and loss at low temperatures. I will discuss two topics. The first topic is the use of superconducting flux qubits to measure magnetic flux noise. The second topic is the measurement of microwave loss in amorphous dielectric materials. Experiments with superconducting coherent systems can be used to extract new information on flux noise and dielectric loss, not accessible using other methods used in the past, providing useful input to theoretical developments.