Hi Sam,
If the client's not able to downgrade to Win 7 PRO there are options to make Windows 8 act and feel like Win 7.
http://blog.laptopmag.com/make-windows-8-like-windows-7Hi Doug,
We have a Win 8 machine in the office and desktop mode is very much the same as Win 7 without the start button. The graphics may be slightly different with flatter looking windows but functionally it isn't much different. The taskbar is there and windows explorer works pretty much the same way. I used desktop shortcuts and had Adagio modules on there working fine. With the 8.1 uprade, you can skip the metro UI on boot up and run pretty much exclusively in desktop mode. The link I posted for Sam is an app that apparently disables some of the annoying things about Win 8 and gives you a start menu back. But I haven't used it personally.
Don't get me wrong, I prefer Windows 7. But if people have purchased the machine already and can't get a downgrade, it's not the end of the world.