Reply #4: No, because...

[regnaD kciN]

...it isn't the fact that the photo is in LAB mode that changes it, it's the modifications you can make via tweaking the curves of the a and b channels. The image is changed through those modifications, and going back to RGB does nothing to change that.

There's an article on post-processing in this month's Outdoor Photography that mentions this technique as an alternative to playing with Hue/Saturation in RGB -- supposedly, it can do the same thing as increasing the saturation, but without the artifacts of that method. There's also an entire book, Photoshop LAB Color: The Canyon Conundrum and Other Adventures in the Most Powerful Colorspace, on the subject of color correction using LAB mode. I'm on the waiting list for it at my local library, and will report back once I get ahold of it.