Sorry Mike, I have to post against you just a little.
I use the sticks every now and then. They do give me a mental push when I see medium to dark purple, so I don't see them as a waste of money.
A little about Ketones. When I was on the Atkins diet I really researched ketones because I heard they would harm the kidneys, when your kidneys are processing ketones, you are considered to be in Ketosis. What I found was this. When fat is being used as energy from your body, it has to be metabolized just like our food does. Our body will use the energy and disgard the rest. This process takes place in your kidneys. It is a lot of work for your kidneys to break down the ketones before sending them to your bladder, so long periods of high ketones 'could' overwork your kidneys.
On the Atkins I stayed in dark purple (they suggest you use them everyday). The Anti-Atkins were reporting that the ketones were just dietary being processed because of the fattening foods. I did a test on myself to see if the ketones were actually my fat or the fat from the diet because it was an all fat diet. I took myself out of ketosis and then I ate only chicken for 3 days and then tested again. I kept my calories low and fat less than 10 grams a day. I was back in full ketosis. So, it really is body fat being deposited and not just dietary fat.
So, the darker the stick, the more fat you are processing. I have also found that it is easier and harder for some people to get into large Ketosis. There are also other things that will affect it, like too much caffiene, your body will use the 'high' off the caffiene before having to go to your fat stores.
Hope this helps.
*I am not a expert in this matter, just sharing what I have found. Do not follow my advice, do what you need to do.