GUI's come in different shapes and sizes. Most people are familiar with Windows, along with the Mac & Linux. These graphical user interfaces defined the way we interact with machines. As processors became smaller, more powerful and cheap almost every electrical gadget has some form of user interface. Whether it be Windows, where the user controls everything from a click of the mouse, or a radio with the user selecting stations from the turn of a knob; the important factor is usability. A whole product can be ruined by a clumsily designed user interface.
Any developer who has worked in the electronics market would agree that a products GUI usually ends up as a last minute addition developed by whoever gets the job. Only a few of the large companies, such as Apple, have put time & resource into their GUI front-end for a set-top box. Whereas in the 'black' goods sector, all development is done as cheaply as possible, hence most GUIs are either off the shelf being developed by the chip manufacturer or a quick addition with no real thought.
Think back to the last time you accessed the menu system on your television. Think about the experience. You probably found it was quite simple, nothing special and probably unintuitive, even painful to use. A good GUI doesn't have to flash and whizzy like Apples, it can just be easy and simple. One compliment for a GUI developer is when someone uses the product and doesn't even comment on the GUI. This would mean the user found the menus natural to use and didn't notice the experience. If a user says 'wow, great GUI!'; then that is an added bonus, normally reserved for the big boys with powerful graphic chip sets.
During the great UK digital TV switchover scheme, I had the pleasure of working on one of the set-top boxes required for the scheme. Being quite old technology there weren't many processor cycles left for any wow factor and the box needed to be used by the over 70s. So by keeping the design clean and the menus simple we managed create a very usuable GUI which even won an award.