By 'pink stuff' I assume you mean saccharine, I would assume that any non-calorie, no carb (or super low carb) sweetener is as acceptable as the next for the purpose of counting carbs. Be advised that some artificial sweeteners mimic symptoms similar to MS, my aunts doctor told her she had to stop using artificial sweeteners for some number of weeks before he could be sure of her diagnosis.
I found a reference to stevia in an old version (2000) of Atkins book, almost in passing towards the end in maintenance he suggests using stevia as a sweetener when confronted with cravings. However he did not go into how much was okay or anything like that. I believe this book is a revised version of his 1997 book, so stevia was still getting established in the US and he may not have had extensive information on it. I still haven't scraped up the money for some pure extract, but hopefully next month.
if the link below works it talks about the different sweeteners, not including stevia.
http://www.bami.us/Diet/ArtificialSweeteners.html