I'm in the middle of my second round of P90X. It is GREAT for stress relief.
I've stopped doing Ab Ripper because I read somewhere that intense abdominal workout is not good while flaring. But the arms, chest, plyo, yoga, etc all do fine with me.
I know for me personally when I do weighted abs, I usually have to go the restroom after the workout or next day a little more. Its also incredibly hard to get rid of ab fat though for me. Seems the fat wants to protect my abdominal region..