Yes, I have. I've used them to help set up my street team on FB, and am currently using one for setting up a blog tour for one book, and another for sending out reviews for my first self-published book coming out in April. I could send out the eARC's myself and keep track of it all la la la, but I would rather use this particular companies service because I know they have inroads with many of the review sites and they have a moneyback guarantee. If at the end of their service I'm not satisfied, I don't pay. But in this case I'm paying it now because I know they will do a good job.
The one setting up the blog tour has been awesome. She handles all the bullshit of contacting the blogs, setting up if they want an interview etc, keeping track of who needs what when, and bugging me because I'm a SUPER procrastinator at doing guest blogs. I hate blogging but it really does help to get my face out there since I don't have my own blog. Plus, she offers the book for review to each review site so that helps as well.
Feel free to ask me any questions you want in a PM.