Our thinking is similar to Jessica's-- I do not trust Nabisco or Pepperidge Farms to label for low-level XC with pn/tn simply because they share lines without disclosing that on labels. Kraft (and subsidiaries)-- a special circle of hell all its own shall be reserved just for them, since they won't even reveal the information when you call to ask.
I've begun to suspect that General Mills doesn't either, so we've become rather wary of them wrt breakfast items like cereal, though I definitely still use Gold Medal flour.
On the other hand, they do label VERY well for intentionally included ingredients, and their allergen handling must be very good indeed, since so few people have problems with them, and so many people DO use them (Nabisco, PF, GM, Kraft). Some of them also treat sesame as a priority allergen-- which is HUGE if you must avoid sesame.
It's really individual. DD's reaction threshold for some nuts is crazy, very crazy low-- and she HAS consistently reacted to Kraft products that 99% of people with her allergies use regularly without any trouble at all. But we don't trust 'em. Reactions trump any rationalizing I can do there-- they may not have ever TOLD me why it is that my kid can't eat marshmallows, in other words, but that doesn't mean that I don't know that they are quite regularly contaminated with one of her allergens.