Some people seem to be averse to running multiple factor for this reason, although in practice I have not seen any issues personally. the AD converters in the factors are very good at what they do IMHO
I think it's just a psychological issue (or at least it is with me). I've never had any problems running all four Factors together, either. And yeah, the converters in the Factors are as good as I've seen in any pedal and better than most. Better than a lot of low-to-mid-range studio equipment, too, IMHO.