What are the side effects of aspartame, stevia, and other sugar substitutes?

One quick update:  Two weeks ago I was interviewed by the great folks at A Sweet Life.  Their site is a great resource, especially for folks with diabetes, but really for everyone (I had the most incredible appetizer on their recommendation this past Sunday).  Here’s a link to the interview.
Ok, on to the issue of the week.  Once you realize how harmful sugar is (by sugar, of course, I mean sucrose and high fructose corn syrup or HFCS, primarily, …