tl;dr heroin and meth together is pretty awesome - gives you the best of both drugs and the negative effects are canceled out.
I love the euphoria of opiates but due to the nature of my job I cannot waste time nodding off or being drowsy. I need to be 100% there and be able to make decisions, advise people, write reports and so on (im not risking anyones life or anything - its not that kind of work).
That's where meth comes in. By itself it is a horrendous drug, imo - leaves one hyper focused and horny to the point of not being able to get anything done. Add some h to take the edge off and its a beautiful, clarifying drug.
Now I know some of you will say that mix h and meth is dangerous, and you are right, but probably not for the reasons you think. The dangers of speedballing come from the heroin - the coke wears off and suddenly the heroin dose is felt at full strength and you od and die. The key factor here is how strong the heroin was to begin with - it would have killed you if you hadnt mixed the coke, which only prolonged the inevitable.
I dose separately and avoid needles to avoid this problem. I find plugging bth is my preferred route as I dont have to worry about fent and honestly plugging makes it hit you strong as hell. I also dont smoke meth, but snort it.
You party hard.