The thing about cinnamon is it's much cheaper in the grocery aisle. It tastes great added to baked goods, warm breakfast cereals, tomato sauces, etc. There's nothing magical about putting it in a capsule, just more expensive.
Personally I take a chromium/vanadium supplement. Some daily vitamins such as Spectrum include them as well. Is it effective or a waste of money? I'm not really concerned. The price is somewhere between a box of donuts and going to one movie with popcorn. I'd rather spend money on something that might or might not have a beneficial impact on my health than something guaranteed not to. A glass of water and a dose of a typical supplement cost about as much as a diet Coke or a cup of coffee. As far as I'm aware a diet Coke or a cup of coffee do nothing for anyone.
Are these measures working? Hard to say whether it's them, the low carb diet, the flax and primrose oil, the Alpha Lipoic Acid, or all of the above. When it comes to diabetes options I prefer to have 'all of the above' available to me.
Do I notice my bgs plunging after taking any of these? No, other than presumably medications, only exercise and alcohol do that for me.
If you're already using cinnamon in your cooking and taking a daily vitamin/mineral supplement you may already have your bases covered.