I have Odoo v8 setup as multiwarehouse and configured to work with multiple Opencart front ends using webkul's Opencart-Odoo bridge (https://store.webkul.com/Opencart-OpenERP-Connector.html) - we are just finishing testing a development of this that synchronises with Odoo-on-saas (i.e. no modules need to be installed at the Odoo end.) I suspect that we may be still waiting some time before odoo's ecommerce functionality can match what is available in magneto/prestashop/opencart - so this is a pragmatic alternative course of action for those with existing ecommerce frontends who wish to move onto Odoo (eg for the multiwarehouse capability).