My MBP (which I've had for over a year) has a case on it, a keyboard protector, and the like; I also have a case on my iPhone. They protect the gadgets, but add a bit of bulk (and typing difficulty, in the keyboard protector). I've been tempted to take them off, but have left them there because they're not too obtrusive.
One could argue that you'd get a better resale price if your gadgets aren't scratched. I've wanted to take the rubber case off of my iPhone, only to be relieved when the case protects it from yet another unanticipated drop onto a hard floor.
Yet there's something to be said for actually enjoying a gadget without the extra bulk of a case.
So I ask you: Do you put cases on your gadgets, or do you prefer to enjoy them "as they are"?