That's great to know. I read in the XP readme: "Oblivion XP is compatible with any and all mods except those that change leveling settings through script (Progress). It is highly recommended that you use one of the excellent level scaling overhauls out there in combination with Oblivion XP"
With 'level scaling overhaul' the author meant mods that change the leveling of the environment, like OOO, Fran's, FCOM, TIE etc. Mods that change the way the player levels and raises his skills/attributes will not work with Oblivion XP unless they were specifically made with XP in mind. That includes mods like Bofra's, the OOO leveling system (which both would be automatically overriden by XP, so no worries if you use OOO) or any of the other mods mentioned in this thread (which are not automatically overriden since they're heavily scripted, so don't use them in combination with XP).