DRM Hacker Alex Ionescu explained the internals of ReactOS in a recent talk. Ionescu indicates that ReactOS is nearly 100% binary and API compatible with the Windows 2003 kernel, and that they are aiming for full Vista compatibility. Ionescu attempted to demonstrate ReactOS but only succeeded in installing it after two BSoDs. This alone should make it clear that ReactOS is still not ready for prime time.
If you’ve wanted to learn more about the ReactOS internals, then now is the time. There are slides (pdf) released from a recent talk by the lead kernel developer Alex Ionescu, which go in depth about what ReactOS is and how it is designed to emulate Windows.
Source: Slashdot