[quote=I just picked up the May/June2006 issue of "PHOTO Techniques" and in there is an article by "Ctein" (pg.41) dealing with LAB. An interesting segment of this article related to manipulating in LAB and then resetting mode to RGB talks about this process as being 'lossy'. I'll quote the paragraph that deals with that...[/QUOTE]
While there may be a small amount of loss in going back and forth I have never found it to make any difference. But in Photoshop CS2 you would experience no loss if you use Smart Objects. By doing that and by imbedding the orignal image (even the RAW image) as a smart object, all of the processing would always go back to the original image.
But sharpening as developed into almost a religious issue. There are hundreds of techniques and there are whole groups that grow up defending one against another and so forth.
As for me, I use whatever works best for the situation. Not every technique is usuable for every situation. For my general work, I do a two pass sharpening. When I have done my post processing and any selective sharpening as I've already shown in two tutorials, I then often use a second overall sharpening pass using CSPro.