I also prefer separate devices, and agree with burris that combo devices rarely perform their individual functions as well as a dedicated device would do. However, one advantage to having a router built into your ATA is that you can remove your regular router for testing purposes in order to troubleshoot. Since the router is so often the cause of voip connection problems, it's nice to be able to configure your ATA to obtain a routable public IP address in order to see whether the problems go away.