yeah, lab is a pretty dandy space for certain things.
The book "Photoshop Lab Color - Dan Margulis" is very thorough and goes through many techniques for use with the lab color space.... amoungst others, how it is great for noise reduction / sharpening / color boosting (as rjmiz showed), color correcting.... the list goes on.
the book is nice and detailed and goes from beginner mode so everyone can understand to advanced mode which will make you scratch your head, so it is great for everyone. or of course, in stead of reading you could always watch this tutorial

not as much background info or details, but definatly quicker.