Personally I think you would have to be nuts to consider using any of those services. Why throw money away when you can obviously write well and the immigration application process is fairly straight forward? If you pay one of these guys, you'll still have to do the lion-share of the work. They can't produce letters of reference, financial records, academic transcripts, letters of intent etc. for you. You'll end up paying thousands of dollars for templates (which you could find with a 2 second Google search).