oxycontin is very addictive, as is hydrocodone, they are both opiates.
Oxycontin is absorbed more slowly that MS (morphine sulphate) because morphine is given IV for the most part, and oxycontin is taken orally.
Depending on the dose and route you will get very different effects. I have given all my morphine on my ambulance to 10% burn victims and it did not even touch the pain (20mg IV, and 5 min transport). Chronic pain sufferers will also build up a tolerance, which will require a higher dose for the same effect.