Its nice that IEEE has open access journals now. I have published in IEEE Open Journal of Power Electronics and its nice that I can share the paper with random people online that are not in academia.
However, the IEEE open access journals charge a few thousand dollars to publish (and they do not do any copy editing. I really don't know where the money goes....). They get their pound of flesh either way.
I would say the biggest advantage to publishing in the IEEE open access journals is the publication time. My paper took around two months from submission to publication, including one review cycle. A previous IEEE paper took around 8 months and some of the conferences are close to a year between initial digest submission and final publication.