That's usually not good enough since the Boxee Box handles flash website different than the version that you download and install yourself. For instance, many sites on the DL version start in full screen but with the Boxee Box they don't. I think this was done to satisfy content owners but it significantly hampers my experience with the Box.

They do try to do two clever things with the box to make this better: Hit menu and sometimes there is a full screen button, sometimes not. Also, they try to place the mouse cursor over the "Fullscreen Button" in the Flash player, but this is wonky at best.