Had a great experience using ViralSweep. We used the basic $50/month subscription and it worked great. Had a few technical errors but were able to get them fixed very quickly by emailing the company's customer service. Giancarlo was great to us.
This was the first time we have every done a contest so I was very worried about it but it ended up working great.
Another reason we chose to go with this company was because several other competitor companies required you to sign up for a year or six months. As this was our very first contest, we did not want to commit to a year's subscription. Viral Sweep allows us to cancel the subscription at any time.