First of all, there is more than one thing out there called "herijuana".
The Steve Tuck bred line, which is the one that most people are interested in, is supposed to be spelled with an "i" like "heroin"; HerO-juana actually refers to a different strain with totally different genetics, though for obvious reasons they get confused and people misspell these.
Anyway, from what I hear, the good stuff flies right off the dispensary shelves and at top dollar. Lots of places on the West Coast call this one "Herijuana OG", with the "OG" just an added tag to suggest potency.
Like everything else, it comes down to which line, what pheno, and skill of the grower, but when done right, herijuana is super potent, and has earned a reputation as a great medical strain.
"Most potent" is hard to nail down, but I've seen this one tested out at 20% THC+, potentially putting it in the same class as the strongest stuff out there (if not the absolute strongest).
The strain is also known for a somewhat odd coffee-like taste, dense heavy golf-ball like buds, a low-to-moderate yield, and a super-stony high. Some people really don't like the taste; some just find that this one puts them right to sleep or gives an instant "couchlock" and don't enjoy the effect. I don't know the numbers here, but I'd imagine this one is relatively high in CBD, making it more suitable to medical use (vs "recreational").
Seeds can be a little tough to come by. Different breeders have offered slightly different versions over the years, with times when the cut wasn't commercially available and "clone only". Right now Sannie's offers the line, though its out of stock and expected to remain that way for several months. He does have several other hybrid strains based on herijuana that are available, though. "KO Kush", and "Anesthesia" are two that come to mind, and he has a few others.