The First G-APD Cherenkov Telescope (FACT) has been constructed as a field test for novel silicon-based photosensors in future telescope arrays and to monitor bright TeV Blazars. Geiger-mode avalanche photo diodes (G-APDs, also known as Silicon-PMs and MPPCs) exhibit several advantages compared to the currently used photomultiplier tubes: good quantum efficiency together with mechanical robustness, low bias voltage, absence of ageing, and very stable signals. The 4.5 degree FACT camera consists of 1440 G-APD pixels, each equipped with a specially developed solid light concentrator. The trigger and data acquisition electronics based on the domino ring sampler chip DRS-4 are fully integrated into the camera. It was installed in a refurbished HEGRA telescope at La Palma by October 11 2011. Although first light took place under bright full-moon conditions, the camera immediately registered air-shower images. Here, we report on the experience gained with this camera during its commissioning and present first results.