Super Fine v. Normal Compression: SD400
Oh, yes, I forgot to mention about loss from later cropping/resaving. I've always saved pics I planned to alter heavily to TIFF beforehand, just so that I would avoid exactly what you're describing. Given my system, I wonder if on a long trip I should count on my 512MB card holding all my pics...:-) That, and it's quicker to open a 1MB file than a 3.2MB file (at least on a laptop).
600 photos+ > 195