Please, Jim, I find the "tobacco" game quite insulting, especially since I've never smoked and both my parents did and paid the price. Tobacco smoke has always had a clear relationship between its components and health problems. Diet sodas don't, as far as I can see.
Most of us find it a product that encourages a craving for unnatural sweetness
This is a very weak argument, though for some it may be true. The human tongue has receptors for sweetness, and it doesn't really matter what triggers them. I don't see why it'd be worse for a no calorie product to do so rather than a high calorie product. But I already admitted that I'm at best the exception to the rule, and might eventually decide to do without permanently.
As for "strict" this was on the basic tenets of no meat, dairy, eggs, and starch based. Before last fall I had some meat, dairy and eggs on a regular basis, though I was mostly McDougallish. Now there is only the occasional exception, the most recent being having a taste (< 1oz) of pot roast this past Monday, mostly to see how it compared with what my mom used to fix. Frankly I wasn't impressed and wouldn't have had any given a second chance. I think it's adding salt or sauces to meat that gives it any appeal. I am starting to cut back considerably on salt though it's sometimes hard to find stuff without it. But I can sure tell the difference.