Are you able to configure add-on domains by yourself? Or do you rely on "support" which looks like it takes some time to respond.

A GOOD host will permit their users significant levels of server management - particularly when eCommerce is involved.

Again... you need a host that HELPS you run your business. If this one is not up to being your "partner", then go find one that is. It matters not if they came "highly recommended"... if you cannot get the level of management and service you require, they are a hindrance to your business.