The Power Useful Button in Lightroom?

It was Matt Kloskowski who originally tagged it with that name at http://lightroomkillertips.com, and I think he was spot on. Well, maybe it should be "The Most Useful Button in Lightroom?" (with a question mark instead) because while it's certainly debatable, it is certainly one of the handiest, and if you're not using the Previous button yet, check out this short little video on why it's so handy. 

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