I had it briefly years ago. It seemed to help and I had no noticeable side-effects for me personally.
Some general points you may know anyway. No offence at all taken if you've considered all this and my apologies if it's teaching my grandmother to suck eggs. We all have different experiences.
Like many pain medications, and indeed many other medications, it carries risks of side-effects that one should watch out for, including potentially very serious side-effects, and some people have withdrawal problems. That being said, if we never took medication that has a risk of side-effects, we'd never take medication.
I am biased in my views because for many years I had hideous chronic pain from arthritis, and finally worked out that for me personally, medication made it worse rather than better, and that thinking techniques helped me best.
(Ignoring it is no good for my particular personality. I have to briefly focus on it, maybe a few times a day, and reassure my subconscious that the 'alarm' sounded by the pain is a 'routine test of the alarm' not a 'new emergency'. My brain then seems to be able to ignore it for a while. Others would find that made it worse and have to focus on ignoring their pain.)
Also, I know from the combination of research and from family experiences in relation to other drugs (e.g. SSRIs) that when people say they have different positive/negative effects and different side-effects from the same medication, it's a genuine potential issue for people, and often relates to things like available enzymes in the body, which may be genetic or may arise from what else is being taken/eaten. (Think of how grapefruit is a problem with some medicines.)
So I'm a very strong believer in watching out for one's own symptoms and being very aware that what helps one person may not help another and vice-versa.
I hope that you can influence your friend to keep an eye open for problems, and perhaps take into account problems with other drugs, e.g. what issues he had with the morphine, and explore what other things besides drugs might help, without being prescriptive about it, and whilst perhaps reassuring him that you know people (here) who've said it's helped them.
That being said, if I'm saying what you already knew, my apologies. I say that because I'm feeling very jumpy today about having asked a question on another site and having felt, perhaps unfairly, that the people there were treating me as if I hadn't thought of the obvious.