Methadone doesn't give you a high, nor is it any more addictive than heroin. What it does do is satisfy the cravings for heroin so that you no longer feel the need to go out and participate in illegal activities in order to fund your habit. This has the added advantage of meaning that you are no longer injecting yourself using potentially dirty needles and putting yourself at huge risk of HIV, Hepatitis, peripheral vascular disease, phlebitis, endocarditis and skin boils/abcesses (amongst many others) which the NHS would have had to pay to treat. It also means that you are able to be relatively stable and hold down a job where you can then be of some use to the economy and thereby contribute positively to a society from which you have taken so, so much. All for the cost of around £1 per day. Seems worth it to me!