Further, if you give your PS to someone on this board to review there is nothing preventing him/her from doing what he/she will with it. Though it wouldn't be nice, Lexylit and Ginatio would face no legal consequences were they to publicly expose your personal statement to the entire group, or decide that your PS is darn good and use it for him/herself in his/her own LS applications. By going through Kaplan you are more assured of confidentiality.
Further, just as the best baseball player isn't always the best baseball teacher, so too good writers do not necessarily know how to communicate good writing skills to others. I would imagine Kaplan to some degree tests the teaching ability of the people they employ to review personal statements.
But to answer your question, no I have no experience with it. And to "sixthify" the question, I would also be interested in anyone who has used such services.