After trying the free version, I elected to purchase the pro version mainly for the SEO friendly links. The seller's website states things like "when you complete your purchase you will be required to submit the domain you plan to use the LinkExchange WP Pro plugin. We will send you a key and you will off and running with the best link exchange plugin for WordPress sites." and "click here to buy and you will be emailed login info to download the LinkExchange WP plugin files."
This was a Palpal purchase which led me to believe that it would be an automated purchase. Once the payment was complete, I assumed I would receive an automated email with some kind of key and login info to download the plugin. I was wrong!
A few hours after the purchase I received an email requesting my domain name. I replied to this email within 5 minutes of receiving it. That was 4 days ago, and is the last I've heard. I have sent 2 more emails, both have been ignored.