In E-Learning, the emphasis is often on technical aspects, and the reason for using technology - the desired pedagogical added-value - is in danger of being neglected. The emphasis of this paper is on the actual process of learning, the learning in E-Learning, and how this process can be assisted by interactive educational software. We briefly present five high-level quality criteria which good educational software must satisfy. Two examples of such software show that a high degree of interactivity has its unavoidable price. We discuss the tradeoff between interactivity and cost of development, making the point that interactive learning environments can not be developed with general purpose authoring tools or learning management systems, but instead require extensive, domain-specific development effort.