Over the past two months I've been working extensively with the open source virtual learning environment (VLE) Moodle. I've been using it in three ways:

1. To provide support for a predominantly classroom-based course (pre and post course activities, forums, wiki, etc.).
2. To support a predominantly online course in the usual way.
3. To build an online community for a potential audience of many thousands of course graduates.

Starting as a complete beginner, I have found Moodle extremely easy to learn (in spite of pretty awful online help) and I have been able to create what I want in surprisingly little time. The system is essentially free (although must be hosted and supported by someone, whether that's your own IT people or a third party such as pteppic.net), but is easily customisable and configurable and offers the following:

• Forums
• Real-time chat
• Delivery and tracking of SCORM-compliant materials
• RSS news feeds
• Wikis
• Glossaries
• Messaging
• Calendars
• Quizzes
• Audio, video, Flash support
• Assignments

The only features I'm really missing are a survey/questionnaire tool and a facility for learner blogs, both of which are in the pipeline.

My question is, what am I not getting that I would with Blackboard, WebCT, FirstClass and other VLEs? What would I get by upping the investment to tens of thousands of pounds, dollars or whatever. I know I'm using it on a relatively small scale but, as I understand it, the Open University are switching their quarter of a million students to Moodle, so it must be a scalable solution. Please tell me, where's the catch?