Anyone have any experience using Channel Online, VarStreet Estore service

Has anyone had any experience using any of the following Estore subscription service providers? ChannelOnline, VarStreet, VarCommerce or Inventory Source.
I would like to use one of the above services for my estore but I am not sure which one would be the best to go with. Does anyone know if a comparison or review was done recently amongst these or other Estore service providers?
I am also looking for a merchant service provider that can offer me great rates without a lot of additional fees and that can provide excellent service.
Anyone have any recommendatons as to who would meet this criteria and where I can purchase a credit card terminal at a reasonable price?

Thanks,
Al