What do you think should be top criteria when designing professional e-learning courses (Both synchronous or non-synchronous)?
The most important thing to remember about providing professional e-learning courses is that there should be a consistent alignment of learning theories (e.g., behaviorism, cognitivism, critical constructivism, connectivism, etc.), methods (synchronous and asynchronous), and multimedia (web 2.0/3.0 tools, software, etc.) that is conducive to forming a learning community that takes the learner from being dependent, to independent, to finally interdependent. Such a learning community would be "open, diverse, interactive, and autonomous" (to use Stephen Downes's words).
I know, a broad answer (to a broad question), but we need to consider the whole ball of wax.
Note: I'm avoiding a detailed description of the method (synchronous and asynchronous) because it's only a third (actually less in my opinion) of the real issue: aligning learning theory, method, and media. These three impact each other as in it's all or nothing. We can't talk about one without mentioning the other two.