OP,
for your information, Muhammed Ziauddin never goes to dental school. he basically got in some schools but decided it is too expensive so he didn't go. His stats were pretty impressive, which played a major factor in admission process along with EC. so I am sure anyone with his stats and EC and only above average Personal statement will also get in. You can write above average PS by using help via PM on SDN. This is on a humble side. If you take advantage of SDN properly, you will be able to write good PS without needing to use any service like him.
Muhammed has no credentials to call himself a dental coach. He tried to use SDN to advertise for his website before but that didn't work out too well. so I think he is doing the PM route where he will PM people to offer "paid help" if needed.
on the side note, admission people spend less than 5 minute to read your PS. they do not read and analyze your PS. so As long as you get your reason across in that amount of characters they give you to show why you want to go to dental school, your PS served its purpose (be concise, be persuasive, and get to the point) .
good luck and hope the best comes to you
incoming DS2 (finishing up my DS1)