My personal experience using the review exchange network: REVIEWLANCER
The concept is very simple:
1- You can get reviews for free by giving reviews and earning points. Each point will give you a review.
2-You could also pay for reviews.
So far so good...
The problem is that the verification process only requires you to send an screen shot of the game and a screen shot of the review. Some times you end up "getting reviews on the Reviewlancer site" from people that took an screen shot of the review they were going to leave before pressing submit to the app store. Reviews that never made it to the App Store but still depleted your earned points for getting review or your money.
For example Between the 2 apps that I added on the site to get the service, The site shows that I have received 20 reviews but only 10 of those has made it to the app store. And all this was in a period of 1 month and a half.
You can try to reject reviews on the site so they don't deplete your money but the site doesn't respond well all the time and you end up getting charge for reviews that didn't make it to the app store.
I tried to discuss this with them but their answer was that: "they have so many users that its hard for them to remove all the users that don't follow all the process.
I try to contact them via the email they provide but they never responded.
They have a chat but they go offline in the middle of the conversations and without answering you questions.
Nice concept but needs some work.
If you decide to use this site, just keep in mind that you might not get all the reviews you pay for.
In my personal experience, I received only half of the reviews I payed for.