One of the advantages of running Android apps on top of a virtual machine is that, if you port that VM (which shouldn't be that hard since the Dalvik VM is open source), you can use Android apps on any other operating system.
This is how we got the Alien Dalvik from the Myriad Group, which was originally supposed to work on top of Meego, but that plan went nowhere after Meego was scrapped by Nokia. Myriad then released version 2.0, which came with support for many other non-Android devices, such as TVs, e-book readers, and even iPads.
Then we also have RIM, which has made its own custom Dalvik VM to support Android apps on their QNX tablets, only requiring some repackaging by developers. But because RIM never intended to use the feature as more than a bullet point on their marketing handouts, the project hasn't gone very far yet.
Perhaps the most ambitious such project is BlueStacks. The developers of BlueStacks set to bring Android apps to Windows, and now even to Mac OS X. The team was surprised to see that, when they launched their Windows app back in March, they got one million downloads in just nine days:
“Our PC version took off a lot faster than we had planned for. People are spending a lot of time on their smartphones and want the same experience on all devices.” said BlueStacks CEO Rosen Sharma,” By bringing Android Apps to Mac we are breaking open the Apple ecosystem, which has traditionally been closed. Also, Android is struggling because of a lack of tablet applications. Developers now have an incentive to build hi-‐res apps to work on the resolutions like retina displays on the new mac for example.”
I think Bluestacks can be very beneficial for the Android ecosystem. If it becomes popular (and Asus will help with that by integrating BlueStacks into all of their laptops from now on), it means that millions of users will be used to using Android apps on their PCs. In turn, this will push developers to create apps that are better optimized for the tablet/laptop form factor and size, which is a good thing not only for the current Android tablet ecosystem, but also for Android's potential move into the desktop space with future versions.