Keep seeing these around the internets:

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Are they worth it? Looks like it'd be easier to see what you're doing, but not sure how long they last before they get gunked up or if they break easy, crack, melt, etc.? Anyone use/used them and like/hate them?

Thought about giving them a try--I was watching some videos on youtube about making custom headers and the guy was raving about them saying it made it easier to see.

Thoughts?