The effect is not dramatic like a stimulant. It's more like it makes my attention stickier, and allows me to hook into long problems more easily. It doesn't "feel" like anything, just causes a noticeable change in what I find engaging. One weird effect it has had is I completely stopped craving alcohol, news and social media. I usually spend hours on Reddit when I don't have anything on my plate. I'm talking 40k+ karma, multiple posts/comments per day type of addiction. I see multi-day, multi-week gaps between comments on my account now, which is unheard of for me. I know it's a silly heuristic, but it's an example of the behavior change.
I've seen much smarter people than me on Reddit say that effects may take 2-3 days. The supplement itself is pretty cheap, and negative side effects are minimal to non-existent. I am seriously astonished that such a common and accessible supplement has had the impact it has had on me. I personally think the cost/benefit ratio is so good that warranted skepticism can be overcome with a self-experiment.
If it doesn't have an effect, then at least a person can check off the "glutamate-glutamine system" checkbox in their quest to address executive function problems.
https://en.wikipedia.org/wiki/Glutamate%E2%80%93glutamine_cy...