For the exception of the spotlight, most of the lights are very wasteful of caustic photons. Since caustic photons are visualized directly, this facts makes very difficult to setup scenes where nice & sharp caustics are needed. This problem is most apparent with background illumination (texture, sunsky..) and sulnlamps - which are ironically the kind of scene illumination where in reality caustics should be the most strong & sharp. A good caustic map is achieved with strong spotlights directed into a caustic generating surface, but each additional type of light added to the scene drastically decreases the sharpness of the caustic photon map, since causic emission is shared among all lamp on the scene.
For this reasons, I propose to include the ability to disable shooting of caustic photons for each light source - the same way it's done for the portals and texture background (or rather this was implemented in the older Yafa 0.1.2 versions for Blender 2.49 and it's currently not available for Blender 2.5). Each light source should have a check-box that would allow to disable caustic photons for it. This way we could use only dedicated spotlights for generating caustic phenomena. Tweaking the scenes and achieving nice results with glass & glossy surfaces would so become much easier. It would also allow to selectively remove caustics, which are sometimes undesired in some parts of a render.