I've used it a few times, once being when Eurowings cancelled DUS-ZRH and I asked if I could be rerouted to GVA instead of ZRH. I bought DUS-ZRH because it was so cheap (unlike GVA, which is where I really wanted to go) and I planned on taking the train down from Zurich with my GA. It was done immediately with a smile. Arrived in Geneva at about the same time as the train would have arrived, because I had to wait a bit for the flight to GVA.