I've just registered on this forum having googled 'Nutriscales' intending to buy another for a friend; saw the discussion here and just _had_ to contribute! I'm not diabetic but am on a programme to lose weight and reduce hypertension; so, calorie and sodium control are what I use the scales for.
In contrast to some of your correspondents, I have to say that I'm delighted with them. They are precise, have a tare and an accumulation facility so that I can add all the ingredients for a particular meal in one go, looking up the nutritional values and the calories as I go on. The little booklet that provides the codes to enter into the scales to give the details for each food is a very good start but, yes, I do need to use other sources too.
The problems, such as they are, begin there, since so many diet web-sites seem to use databases of irrelevant and not especially healthy US Supermarket packaged foods; but a half-hour (*) or so spent in finding the relevant details is, to my mind, a fair price to pay for eating in a controlled, and may I say, delicious manner! Because of course what all this does (when you've realised that shop bread contains excessive amounts of sodium; that packaged foods and convenience meals are loaded with sugars, fats, MSG and all the rest of it) is that it encourages you to start cooking your own meals from fresh ingredients.
(*) reducing to zero once I've done the search and calculation once, since I record the results for next time. Too busy to add a half-hour to your food prep time? Meh! Cook at weekends, double the quantity and freeze for the weekdays when you're in a rush!
18 months ago I was 16 stone 11 pounds, mean blood pressure (using various medicines) around the 152/80 mark. (Male 5'9" aged 65.) Today I'm exactly 13 stone 0 pounds, mean BP on the same medicines around 115/70, and as soon as I hit the 12 stone 5 pound target my GP set me I'll be discussing how we might reduce some of the medications. The process hasn't been effort-free-- nothing is, in this vale of tears-- but it's been wonderful in encouraging a careful and disciplined approach, and those little scales have repaid their purchase price a thousand times over!