Changing from one system to another or upgrading a system while keeping your business process ON is like changing the tyre of a speeding car while it is running. This is seen to happen easily in James Bond movies but in reality it is very challenging.
You need to know how fast can they implement your automated AP solution? Will the solution be easy for your AP and management teams to absorb? If technical support is needed, can you get someone on the phone right away? The best way to answer these questions is by asking other customers. So request that your vendor provides references—preferably businesses that are similar to yours in terms of size and industry vertical.
Further, will the vendor offer initial and ongoing training to help your staff understand how to use the solution? Will the vendor offer an SLA for resolving support tickets and give you the option to access support any way you want—phone, email, webchat?