GPS Satellites Affected by Relativity

I was reading a Wikipedia article on GPS which made a very good point: given their immense speed, the clocks GPS satellites are affected by relativity. GPS satellites reside in an intermediate earth orbit such that the difference in the speed versus that of the surface of the Earth is quite significant. Due to this great speed difference, the clocks on-board GPS satellites are affected by special (as well as general) relativity and as such differ from a clock on Earth's surface by about 38 microseconds per day. For anyone who has ever been interested in relativity or quantum theory, this is an amazing example of relativity in a real-life and thoroughly used system.