Thanks for sharing all this info.
I have been thinking of doing this as well, I can see where keywords would make it so much easier to find a set.
I have picasa but just haven't sat down and played with.
I also really like excel,How do you link a photo/image? and do you make a column for each of your keywords?
I have never thought of an inventory labelling system for my stamp sets, except the crate or drawer they are in is labeled- christmas drawer, words, alphabets, masculine, coordinates with punches. Like you say so many fall into more than one category, they tend to get shuffled around, your filing system makes sense (mine are mostly SU wood mount, so I could label the clamshell to correspond with a number). Currently I flip through them on my computer, I am so glad I have always scanned every set when I bought it. BUt I am also glad I printed a copy to put in a binder, because before my computer crashed it must have been starting to delete some images, I am sure I had scanned them all, becuase when i reloaded my backup some where not there, thank goodness I had a paper copy too (that is the only time I have really used the paper binder). The computer is much handier.