I downloaded the community technical preview (CTP) of the next version of Visual Studio.NET ("Orcas") the other day. I was startled to discover that at the end of the download, what I had was a virtual machine image, not an installer.
Virtual machine technology is what allows you to run a different operating system on your machine without rebooting - it simply runs as an application. Both Microsoft, and the ruling king - VMWare, are investing heavily in bringing this technology to more common uses. It's been around forever, but only in the last couple of years as it been seen outside specialized areas, such as testing or software evaluation (note, Try LabVIEW is accomplished through virtual machines hosted on a server).
I'm very curious to see how this CTP sequence plays out. The VM software from Microsoft is free, updates are smaller (VM's support "diff" hard drives, which contain only the changed sectors and merge with the original) and I don't need a dedicated machine to test it on.
The downsides are that the first download is huge (3Gb for VS.NET - must include the OS as well as everything else), it takes a beefy machine to run a VM on top of it, and you don't have access to hardware (except the common things like network cards)...this last is a bit of a problem for us here at National Instruments :)
So it raises the question - would you want to try out software, either for evaluation or for betas, via a virtual machine? Have you had much experience with them? Let me know.