I have been utilizing Kratom on and off for many years, since 2009, so I have quite a bit of experience with it. Unfortunately its effects became drastically weaker since I got CFS in around 2011-2012. I suspect some of my receptors have been damaged by autoantibodies because I'm also immune to the effects of classic opiates (and so if my wife, who also has CFS, which is quite a coincidence).
As far as effects, I don't have pain so I can't comment on that. For me it helps with depression and anxiety. It used to help with sleep too but that has disappeared. I take it as needed. Kratom contains some of the same alkaloids as Cat's Claw, chiefly Rhynchophylline, so there is a good chance that it is also an immunomodulator. There is anecdotal evidence (unfortunately good studies are very rare for Kratom) that people taking Kratom daily get sick much less often with flu and colds. There is also pretty good (again anecdotal) evidence that it's very safe, since there are a lot of people on the Kratom forums who have been consuming it daily for many years and had bloodwork done that consistently came out perfect.
In regards to the risk for addiction that some bring up as a reason for concern, frankly you are more likely to get addicted to coffee than to Kratom, as long as you choose PLAIN LEAF and stay away from EXTRACTS. This is very important! The Kratom plant contains a very unique makeup of alkaloids some of which are agonists at opioid receptors and some are antagonists. So when utilizing the leaf with its full spectrum of alkaloids, not only the potential for addiction is very minimal (and who would get addicted to it probably is one of those people with a certain brain chemistry that makes them get addicted to most things, food, coffee, work, adrenaline, etc), but the tolerance doesn't really increase easily. It's pretty common for people who take reasonable amounts of Kratom to stay on the same dose for months or years without it losing efficacy. One more thing about plain leaf is that it has an anti-abuse mechanisms built-in: if you try to take too much you will get very nauseous and vomit, therefore eliminating the excess. And if you try to redose often, it progressively loses efficacy, so you can't keep taking it constantly.
Extracts, on the other hand, are bad news, because they don't contain the full spectrum of alkaloids and most importantly they allow people to consume much more of a given alkaloid than they ever could if they were working with plain leaves. I mean, everybody knows coffee is safe to consume, but start taking pure caffeine pills and see how quickly things go downhill, both in terms of addiction and harmful effects!
Bottom line is, Kratom is very safe as long as plain leaf is used and extracts are avoided. Don't expect any miracles but it might help with some issues. If you are especially interested in opioid antagonists, the stem and vein material is probably your best bet. If you have specific questions drop a message. Additionally the Kratom Forum is a wonderful place to learn about Kratom, and it also has an area with approved vendors from whom you are guaranteed to get high quality stuff at honest prices.
http://thekratomforum.com
BTW the DEA tried to ban Kratom a few months back and there was an uproar (a lot of people taking Kratom have chronic pain or are recovering addicts for whom Kratom saved their lives). Now the situation is unclear and we are waiting for a ruling. I'm saying this because if you ever hear about Kratom in the news in case an agency tries to ban it again, please consider contributing (with petitions or letters to reps) to fight whatever nonsense the agencies will come up with. There are a lot of people who, like us CFSers, suffered a lot and had no help from the medical community, and found a solution in Kratom. They deserve to not have that taken away from them!
