Just a quick question with regards the subject above, there has been alot of recommendation to do operations like levels, noise reduction and (especially) sharpening on Lightness channel on Lab Color mode. But would it not be the same if I continue to do them in RGB mode then set blend to luminosity (since i do everything in layers anyway)? Too much hassle (and limitation) associated in working on Color Mode or lots of toggling (and flattening).

Also for CS3, can i assume that 3rd party filters would not be able to operate as smart filters? If it's possible, how do you do it?

Thanks in advance.