The satellite system of M31 is the next closest satellite system to our own, and is well within reach of current generations of ground-based instrumentation. We have conducted a survey of this system with the Isaac Newton Telescope Wide Field Camera, particularly focussing on the seven dwarf spheroidal companions, and derived homogeneous, fundamental information for them. This reveals the presence of severe tidal distortion and multiple structural components in some systems. In addition, a comparison of the M31 dwarf spheroidals to their Galactic counterparts shows that the M31 dwarf spheroidals have scale radii generally twice as large as the Galactic dwarfs, suggesting that the tidal field of M31 may be substantially weaker than that for the Galaxy. A Keck/DEIMOS study of the newly discovered satellite And IX suggests that this galaxy has an anomalously large metallicity for its luminosity, and shows it to be strongly dark matter dominated.