This paper theoretically examined how key success factors (KSFs) of new product development process, as a new dimension of marketing concept and value creation, could be exploited through learning outside the firm or through customer involvement in key stages of the development process. Such collaborative relationship- though suffers scholarly neglect in Nigeria, costly and perhaps difficult to apply and more profound in B2B than B2C transactions- is benefiting in terms of manipulating the environment to a firm’s advantage through having products that exactly meet the aspirations of the world of customers, though consumers are erratic and rarely verbalize their needs with precision. All things being equal, user involvement reduces large inventories and distribution costs, minimizes product returns, builds strong customer relationships, matches production with consumption patterns, promises customer willingness to pay premium price, makes managerial decisions flexible, and above all achieves the ideals of TQM, and perhaps marketing concept. However, different firms benefit from different forms of user interactions subject to top management idiosyncrasy, market power, and competitive environment. Often the extent of disruption on established behaviour pattern (e.g.; radical and incremental concepts) determines the measure of customer interactions. SMEs follow distinct action rationality, leading to rapid implementation of some user inputs, and defensiveness towards others and larger firms are more exposed to user inputs because of their supposedly huge and better resources, yet less committed to execute it. Therefore, this paper developed a model of designers and users involvement based on literature. It joins other similar papers to raise alertness on facilitating the spread, and actual implementation, of user involvement philosophy in radical and incremental innovations irrespective of the industry and other environmental variables.