We've recently built a custom Linux desktop image for use as a VDI client with legacy laptop hardware. This means that our customer is re-imaging laptops with a free and open-source CentOS Linux Operating System, running the VMware Horizon client software.
This is a great option for this customer, as they are able to extend the life of laptop hardware and protect their investment, whilst avoiding any unnecessary Microsoft licensing and management costs.
It also has support benefits; any possible user confusion around accessing a Windows VDI desktop from a Windows laptop is avoided as the local Linux laptop UI is completely different from the day-to-day Windows VDI environment. The "kiosk" nature of the image also means that the user is led straight to their VDI login without any unnecessary diversions or options.
We've also found that hardware compatibility is good; a single CentOS Linux image has been successfully deployed to laptops from more than one vendor (Dell and HP in this case).