I have never used them before, and am not a big fan of paying for link building programs. The thing about them is that you are not the only one paying so the odds that you are getting strong links are slim. If you are going to use them make sure that you get a link profile ahead of time that will let you know the link address, amount of outbound links, and where the link will be on the page.
One of the best value for money link building providers would be yourself as you already know what you exactly want. But, of course, you need to a toolset to help you come up with a solid link building campaign, which, I think, the seoMOZ pro software can provide. There's a month free trial to see it for yourself. ref. seomoz.org/plans