I think both positions are fine, vertical or horizontal. As long as...

a) surface of table is flat
b) no obstacles around the console especially the vents
c) the console is not moved when in use - - most definitely the disc will be scratched when moving position

I place mine vertical. I had to because my table top already has the HDTV on it and there isn't much room to place the console horizontal. Just need to be extra cautious when placing a DVD into the tray vertically - - many tend to think the disc is properly on the tray but it isn't. It may drop from the tray when let go.