I've always run trilinear filtering, and now I've added anastropic. Even at the low 2x setting, distant textures are much improved. But I wonder - are they in fact compatible, or is it a question of either / or?

The short answer is to use both together. When you select either bilinear or trilinear filtering together with anisotropic filtering, you are effectively determining the overall quality level of the final filtering. Trilinear + anisotropic provides higher image quality than bilinear + anisotropic. Depending on the quality and size of your monitor, you may not see a great deal of difference between the two, but trilinear + anisotropic is more acceptable to the eye with less graininess.

Many thanks for such a concise reply. Great relief!