The only type of service I would even consider hiring would be a niche link building service. Something like "Medical Link Builders". Then I would be comfortable believing they might bring me some traffic through their links as well.
Link exchange is still worth and work for our sites. And it will help to get back-links. But the things which you have to take care is the relevant product or business. You have to exchange the link from relevant category.
Choose the best site for link exchange with the same niche and be sure that your website is quality to be worth it for this method.