We've looked at them. There service is pretty slick, and well-backed, but you need to pay a significant monthly fee (with 12 month lock-in) to get started, so

We've looked at them. There service is pretty slick, and well-backed, but you need to pay a significant monthly fee (with 12 month lock-in) to get started, so you would want to have a good turn-over before going with them. They seem to be set up for this scenario, offering services to change over from your previous system.