Yes, I use that technique and variations of that technique pretty regularly in combination with levels and curves. I agree that it often adds contrast differently than using levels or curves alone. If you set curves/levels blend modes to luminosity you can get close though.
Alternative methods to achieve similar results would be to copy and paste either the red, green, or blue channels and set the blend mode to softlight, or just make a duplicate layer (or stamp visible: ctrl, shift, alt + E), and set blend mode to softlight and desaturate the layer if necessary. Though I think the channel mixer approach gives the greatest level of adjustment.