@Sarg: easy explanation (and Tom maybe you could post it, if I'm not missing something)
Everyone starts with a GR of 100. When you sign up for a game, instead of putting in a fixed number of points, you're putting in 2/35 of your current points. The points in the pot are divided as they normally would be at the end of any game. So the higher-rated players in a game stand to lose more, and gain less. In a recent game, for example, I was one of the lower-rated players in a 5-way draw. My GR went up about 10

--the top-rated participant got maybe 2.