thanks for the note about LearnDash. You are right, WP is a great platform for learning management, in particular because of the social aspects it can afford. I'll respectfully disagree with mhathaway about the level of metrics that can be obtain in WP vs. other platforms, such as Moodle. In the past, this statement would have been true. However, with the new tin-can api (replacement of the old SCORM protocol), gathering learning metrics isn't limited by the Moodle-esque infrastructure.
We are currently infusing tin-can api into the LearnDash plugin, which essentially means it will gather data that people are used to seeing in traditional LMS platforms. If you are interested in reading more about tin-can api, head over to Benefits of Tin-Can API | WPLMS .
If you like Learn Dash, did you see the recent launch of WooTheme's Sensei LMS plugin for WordPress?
I think it all depends on how you want to use your VLE. WordPress based solutions provide a 'lite' option. But they lack most of the sophisticated assessment, tracking and analytics capabilities of something like Moodle.