[cogitator]

I answered my own question by doing a bit of reading.

All of the pages (1-8) are interesting, but this one discusses spin-off benefits:

The Surprising Spin-Offs from Gravity Probe B: Schiff's Cargo

One of which is a better geoid (standard reference gravity surface) of the Earth, providing better sea surface height and surface change data.

[RightWingAtheist]

Great link!