I'm probably a latecomer to this particular party, but I recently read Steve Krug's "Don't make me think".
If you're not familiar with this great book but you design elearning, or work with it, I really suggest that you at least spend an hour down your local Borders and flick through it (it's so well put together that you'll get most of the take-away points in that time). Krug is a web-usability expert, and since the publication of the first edition of this book in 2002, I think he probably deserves the epithet "guru".
Krug central premise is summarised in the title of his book - anything that makes your users think twice about anything other than what they are trying to achieve when entering your website is an error. For Krug, the enemies of good design lie in splash pages, deviant navigation, unnecessary words, buttons that don't look like buttons (and non-buttons that do), CEO-inspired "wow-factor" - in fact, Krug's enemies are, by and large, enemies that should be common to elearning designers.
Krug's lesson is a simple one, but one that segues neatly with the work of elearning sciencey types like Clark and Meyer. Where Krug sees a fraction of a pause and a loss of good will, Clark and Meyer would probably sees cognitive interference.
One part that really struck a chord with me is Krug's advice to try to stick to recognised navigational patterns. As a reference he unapologetically refers to Amazon's way of doing things - many of the best facets of commercial web-design are on display there - if perhaps they weren't devised for it in the first place.
I'm doing quite a lot of rapid approach content of late - mostly with tools like Articulate - and one good feature of these tools is the interactions are quite straight forward; the learner soon forgets about the interface and can concentrate on the learning. At the same time, reviewing a couple of courses I wrote a couple of years ago I can see some instances where "cool" interactions I thought up to explore content are more than likely going to cause my learners to blow a fuse, or at the very least break the flow of their learning.