The best feature is that it makes things easy by providing an integrated view across all aspects including but not limited to inventory control, stock procurement etc.
It has lot more features like integration workflows between modules, customising screens/views as per need, customization options available within NetSuite itself are few other good points I have experienced so far after using this software over past one year. None at present time. We use netsuites mainly for financials purposes only; we do not really utilize any additional functionality offered through third party integrations or APIs (like Salesforce).