A very good discussion of the use of the word persons is found in Chan's book. I will submit a shameless plug for it here. I have it and read it. I think it is worth mentioning here. Chan certainly has deep roots in Oneness doctrine and his handling of the controversial "persons" is worth the read.
I do think it very true that most Trinitarians don't know what Oneness beliefs are and vice versa...notice I said most and not all.