I just posted a similar question, as I have been searching myself for a while, and want to find the absolute best program I can, and want others to have the same. After using services like tenant background, rent prep, etc, I found a really helpful and kind service that I've been using ever since.
It is called TenantMagic, and provides me with a free and incredibly simple tenant screening service. As one of my must-haves was customer service, I called the number listed on the website and in a moment was talking with the company's owner about how they can be of help. I used the service for one of my clients to see, and I was totally impressed.
For anyone still looking, or even for anyone not 100% satisfied with every aspect of their current service, I would highly recommend TenantMagic.
Even if you are satisfied, give the owner a call, he's an incredibly kind man and happy to help.