Because I'm a total klutz, and have an irritating habit of sneezing during this allegy season, my ipad is in a protective case (a survivor, by griffin technology). Aside from the decreased tolerances on the 30 pin port, which makes it difficult to plug in anything besides the sync cable, it's mechanically sound.
The raised bezel makes it difficult to use the "swipe" gesture, and it is heavy. But from a Jobsian point of view, the screen protector is probably the worst element. The Ipad has an absolutely beautiful screen. The thin layer of protective plastic is dull, and not as transparent. As a result, the ipad's graphics are muted.
Glass has an optical advantage over plastic. Moreover, the right kind of glass is used, it doesn't scratch like plastics do. It does, however, shatter. Gorilla Glass, and the various alternatives are an attempt to get all the desirable advantages of glass and of plastic (aside from price), and incorporate them into a single material.
As for LCD TV's, they vary widely in quality. Supposedly, Plasma (which uses glass) can have a substantial advantage over LCDs under certain conditions. I'm not sure what my LCD TV uses, but I know my Imac uses a glass screen.