Let's first look at OpenArena on the Core i3 2100.
The Linux 2.6.39 DRM boosts the Sandy Bridge performance nicely, but the set of six LLC caching patches ramps up the performance even more. Going from Linux 2.6.38 to 2.6.39-rc1 yielded a 19% frame-rate improvement on average, while tossing in the six LLC caching patches increases it an additional 12%. This means going from a vanilla Linux 2.6.38 kernel to the latest experimental Intel code yields a 33% boost in total. This delta is not even factoring in the Mesa fix earlier this month that squeezed out other significant gains.
The gains for the Intel Core i5 2500K are even greater with a 43% boost in OpenGL frame-rate performance between the 2.6.38 kernel and Linux 2.6.39-rc1 + LLC Caching.