Id adds one hop (our appliance) to the path. It tries to increase performance of your path by taking non-standard BGP metrics into account: congestion and latency
Where is it physically located, what about congestion of the appliance itself, what are your peerings?
What does transit mean in this context; like between my VPC and your appliance? Can you give an example for e.g. an AWS region?
How is the appliance implemented, is it physical hardware, EC2 instances? Is it redundant, how do you scale it in terms of bandwidth?