My wife and I live in Switzerland for the accumulation phase, but we will probably move back to Germany when we are FI.
Switzerland is ideal for accumulation because the overall wage level is ridiculously high. Prices are also high, but saving 65% of a huge salary means a faster-growing stache compared to saving 65% from a merely decent salary.
If German Mustachians would decide on a city to live in, this would influence our decision on where to settle down once we get back to Germany. I imagine several streets inhabited mostly by Mustachian citizens, with the Mustachian Party getting a few seats in the city council, lobbying for bike-friendly city planning and a well-stocked public library. ;)