In my experience with Opana, for me the positive was the no question about it, deep pain relief. If you take the Opana ER, which I'm about to be prescribed, deep pain relief and nice sedation that lasts all day long, like 10-12 hours.
Now for the (subjective) negative points. Depending on your tolerance to opiates in general, this stuff can make you throw up due to how strong it is. The nice sedation that many people like, can be very excessive including severe respiratory depression, like ^^ the poster above me pointed out. This stuff is very strong on its own. Mixing any kind of cns depressant like benzodiazepines, sleeping pills, or alcohol, can easily kill you.
IMO, forget trying to snort, inject, or do anything other then swallow the pill correctly. This medicine is great, but aside from the accidental OD, this is a medicine that you do not want to get strung out on. People say the withdrawal can be very bad.
I'm about to get this medicine prescribed because it works. I've done the research and learned about the risks. I am getting it for pain related to cancer treatment. If I wasn't mature , had any doubt about my ability to follow the directions or didn't have a close relationship with my Pain Management doctor, I would not go near this medication.
Be safe
Speed King.