Well yeah, it's an opiate. If it wasn't potentially addictive it probably wouldn't be effective either. It's not as strong as a prescription pain medication is but it definitely has a similar effect. Just treat it with respect and you should be fine.
Kratom is definitely effective for pain. I have multiple injuries that flare up from time to time and sometimes I'll take a few capsules before I workout in the morning. It's a tremendous help and allows me to stay focused on the workout instead of thinking about the pain. I've never had any...