The ReactOS Explorer basically functions like the standard Windows one, but without all the thumbnail views (which isn't a big loss, really).

ReactOS now supports tiling and cascading windows automatically.

ReactOS does have a regedit tool, but it is possible to browse the registry from within the Explorer. Honestly maybe not the best idea to have it accessible via My Computer considering how dangerous mucking around in the registry can be.

ReactOS now includes themes by default. This is the "Modern" theme.

This may have been present in earlier builds, but here is the ReactOS event viewer.