Future CSCL technologies are described by the community as flexible, tailorable, negotiable, and appropriate for various collaborative settings, conditions and contexts. This paper describes the key design issues of a generic synchronous collaborative learning environment, called Omega+. In this approach, “model-based genericity” is applied to the four dimensions of collaborative learning: the situation, the interaction, the process, and the way of monitoring individual and group performance. These four aspects are explicitly specified in a set of models that serve as parameters for the generic environment. This opens the possibility of combining many structuring/scaffolding techniques that have been proposed in isolation in the CSCL literature. The paper also emphasizes the specificities and difficulties of evaluating a comprehensive generic support approach. Experimental evaluations conducted by system designers generally isolate the effects of a particular design feature on learning. This kind of evaluation can hardly demonstrate the usefulness of a generic model at the global level and the feasibility of system customization by non-specialist teachers. To address these difficulties, Omega+ is integrated into a larger collaborative web platform dedicated to CSCL practice, evaluation (by collecting anonymized logs), and dissemination (by supporting the technical and pedagogical development of teachers).