Since I had some unplanned free time today, I finally got around to posting an updated refractometer FG spreadsheet:
http://seanterrill.com/2011/04/07/refractometer-fg-results/There are some minor tweaks, but the big news is that I was able to collect data from six other brewers, and the precision of the new FG correlation seems to be about on par with the typical $8 homebrewer's hydrometer.