So, it definitely has limitations...but it's power level can be quite enormous at times. I think I'll stick to my previous house ruling that Morphing is a synergy prerequisite (making it a total bonus of +3), and it works just like the transmuting ability says...except you also simultaneously morph your weapon into an appropriate weapon to overcome the necessary DR type. Example: you hit a lichfiend with DR 15/adamantine, bludgeoning & good with a greatsword; next round, at the start of your turn, the greatsword morphs into a heavy mace that ignores the adamantine & good DR. For some reason, I don't have a problem with a weapon ignoring the alignment or special material DR's, but the weapon type (slashing or whatever) bothers me. YMMV. I might also rule that epic DR is immune to this ability.