If you’ve ever encountered a “The Folder Could Not Be Found” message in the Lightroom Develop module or seen a question mark over a folder name in the Library module you’ll love the new Smart Previews in Lightroom 5.
"Do You Use The Tone Curve?" No, but that's just because I didn't understand it until now. I've always done most my edits with the tone sliders. For now on I'll see my black and white points with the tone sliders and then move to curves to and modify the sliders if I need to change any other tones.