Yes, if it installs correctly* on bare metal then one can boot to an explorer-like shell in a matter of seconds without going through a Linux desktop.

But I can see an obvious use case - testing. Customer reports an error but you can't reproduce it on your company's Windows development machines. I was able to reproduce a couple of bugs that way with wine and I imagine it could be handy running under ReactOS.

* I've only ever tried it in a VM.