So, I drink the stuff. Not as much as water, but sometimes I want something cold with flavor without any sugar, and I was unable for one reason or another to make some regular plain iced tea.
As far as I can tell the two ingredients to be concerned about are aspartame and acesulfame potassium. The evidence on the former is mixed. Yeah, it's not paleo. But neither are chocolate, red wine, and coffee, and many of us grandfather those into our regimes. Also, I am under the impression (perhaps incorrectly) that Crystal Light has a lot less of it than diet soda, which is what people are usually concerned about when discussing aspartame.
As for the acesulfame potassium, from what little I can glean the Center for Science in the Public Interest makes a big deal out of worrying about it. But they're the jackholes that got the beef tallow out of fast-food fries and coconut oil out of movie theater popcorn. So my instinct is to always disagree with them.
I am familiar with the studies that seem to suggest artificial sweeteners 'trick' our metabolisms into thinking we ingested something sweet, kicking off an insulin response. But I have not detected such a response in me. Although I am going on how I feel, not actually measuring. But I can certainly 'feel' the insulin response when I eat other things.
So: Crystal Light. Not paleo, but also not worth worrying about in moderation? Or should I really cut that stuff out?