It is cool for all sizes of business, however, there is one significant concern from the payment perspective - Shopify creates a big challenge for the alternative payment methods to be listed in the Payment methods` list. The requirements for P-methods in order to open Shopify API for integration is quite too much, really to much.
So if I have a local method that is not well-known in the world or does not process 10millions everyday - it is almost impossible to add it to my shop.