I did not use Semblio, but I used another similar product that came from Macromedia and then went to Adobe, Coursebuilder, and I participated in the development of the Moodle deployment, a cross-platform VLE (Virtual Learning Environment).
Coursebuilder suffered / suffered from the same problem as Semblio, and these people who can create courses from a technical point of view are not directly related to the design / training of the course and vice versa.
The technical make-up of both seemed beautiful, but in the end he went down before Otaku said above: "Well, we tried, but no one wanted it."
I often feel that when this type of product is designed or discussed, that the support of people seems to be mistaken in online learning using massively polished 3D graphics tools, as well as the presentation of errors for the substance.
As a counter example, Moodle is FOSS, which itself installs a tool intended for use by teachers. When accessing the server on an "amateur" basis, a college teacher or teacher with minimal skills and several nightly readings can install and configure Moodle and take a course for students for several days or even hours. Of course, it may look surprisingly awkward compared to those like CourseBuilder and Semblio, but it gets tremendous use and support. Moodle, of course, is cross-platform and will work at relatively low connection levels and computer specifications, since all you need to power it (in most cases) is a browser.
In addition, the use of tools such as Semblio, which at the same time are perfectly capable of creating completely good teaching materials and training tools, often has no other details. How do you deliver training? Is this part of a broader course and how do you integrate it? How do you celebrate this? and etc.
I sometimes think that the likes of Semblio and CourseBuilder sell technology, Flash, Silverlight, etc., and not as a real learning tool. But I apologize if this opinion seems biased.