I think the issue of having a demo link is a bit difficult. Think of your Microsoft example. Users go there knowing exactly what product they are about to demo and what they'll get from it (a document, a presentation, calculations, compiled code, etc.). We help manage and deliver virtual applications - we make your life easier - but that's a harder thing to show. Surgient is all the things that go around ultimately presenting that image to the end user, from managing the VMs from a resource and scheduling allocation, to reporting on usage, to users management and access control, to image building, updates, and maintenance, to name a few. What we do is all about convenience and assistance to get the customer to the ultimate goal - delivering training, testing, or demoing a piece of software - and those things won't be as interesting to the user without them understanding why they need to do it all. On the flip side, if our demo was as simple as taking them to a Windows desktop in a VM, well, then we skip the importance of what Surgient is really about and the uneducated user may go "so, Windows....big deal".
So, with all that said, it takes me to the question - if we were to put a demo link on the product home page, what would you, as a potential customer, expect to see there that would make you actually pay attention and want to play with it and learn more?