Yes it's definitely worth taking this supplement. It's been proven to have immediate effects and it's metabolized in subsets of CYP450.
The problem is that people are looking for the answer to questions like "will it make my experience with this other substance.... (fill in any blank here)", and that's a largely SUBJECTIVE question. As importantly, you are getting into VAST differences between how any 2 people metabolize things. Even the SAME person will have different experiences based on what state they are in on any given day.
If you have ever had an amazing experience and then using the exact same substance from the exact same batch had a totally different experience another day, you understand what I mean.
The pH of your blood/gut, whatever else is floating around in you, mental state, hydration, interactions between everything from what you ate for the last 2 days to how much stress you are under.... And the list goes on and on.... Will affect the subjective perception of how you feel.
For example, there used to be days when I was on massive quantities of pain meds where 40-50mg if hydrocodone would adequately relieve pain and even give some euphoria, and the next day even 300mg of oxycontin would barely touch the pain and not produce any kind of euphoria or mental effects at all. I found out that I have a rare combination of CYP450 metabolism, but I still could not predict what was going to be adequate just to control things enough to be able to work, nevermind fine tune the experience.
WITH ALL THAT IN MIND, yes, you should absolutely try using agmatine before and during concomitant use of whatever else you use. At the upper limit of what the directions say.
It has pretty reliably enhanced all aspects of all opiates I have been scripted, including suboxone. It has never had any side effects for me, and although I can't prove anything, beyond helping me feel more relief, it also helped as far as cravings to take more of whatever the same day.
Numerous academic papers show it interacts with a variety of metabolism pathways in a positive way, so there's no doubt it's doing SOMETHING. Exactly what that something is will be unique to you. I have found that it does NOT need to build up in my system, and I reserve using it for when I am in extreme pain or craving because right now I am only taking buprenorohine. But when I was using other things I did the same. I would try to remember to take it an hour before, but even up to an hour afterwards it helped provide relief and duration. For me personally it also increased the sedation ("nod") significantly to the point where there was absolutely no chance that it was placebo.
I think that this supplement is one of the most underrated tools at your disposal!