This design even produces a smaller obstruction to incomming light rays than a conventional Newtonian, as the "spider" has become transparent, and the mirror holder much smaller.  Such a drastic reduction in the size of the obstruction caused by the "flat" translates into a much better resolution and a brighter image.  Like all catadioptrics, the mirrors are protected from the external elements.  However it also shares their problems, ie taking longer to acclimatize.
One nice feature of this design over a conventional Newtonian, is the ability to obtain Prime Image Photographs by removing the flat mirror and installing a CCD camera in its place. Put your mouse cursor over the word install to see how this is done.