as far as pain killing effects go it doesnt work for shit after you are stable and I mean that. I just got over this abscessed infected tooth pain sooo unbearable not even methadone could mask it for more than Maybe 3 hours. Some days it just gets you by. I really can only say if you want to get the most out of its painkilling effects eat foods high in saturated fat because methadone just sits in your belly and for me doesnt ever last as long as I need it to anymore
Well, it definitely varies by person. I was on MMT for about 2 years, at my highest stable dose (105mg/day), when I was in a serious car accident (2 broken bones, surgery, metal implants, etc). I certainly noticed a great deal of palliative pain relief 60-180 minutes after taking my daily Methadone dose. Though as the peak plasma levels lowered as the hours past, the pain would gradually become more noticeable until the next mornings dose. As I wrote in an earlier post here, a number of chronic pain patients attend MMT clinics fo a number of reasons (1 being Methadone is a pretty good top-5 chronic pain management opioid, MMT is cheaper than pain management specialists and associated medical professional visit costs, access to clinic counselors, nurse practitioners and doctors, etc).
To answer an earlier question, yes, in some states Methadone maintanence is covered by a branch of Medicaid. Maryland is one such state. They have 2 plans under their PAC program (related to Medicaid, accessed through the Department of Health and Human Services); one which will cover MMT and one which covers BMT (that isn't all they cover; these are health insurance plans for low income or unemployed state residents)- and there are I believe 2 or 3 more plan options to choose from as well, but only the 2 cover ORT programs. It is worth some research to find out if your state offers such a program (though it's best to make an actual visit to your local Department of Health and Human Services; I found the online information of state governments regarding Medicaid-esque programs is sparse, confusing and overall lacking).
EDIT: Regarding cravings etc. For many people, when they first start MMT, even at 30mg a day, and gradually go up in dose by 5mg or 10mg increments, they experience what many clinic FAQ pamphlets call a 'glow' (i.e. you feel euphoric and slightly high) an hour or so after taking your daily dose. However, once your body gets accustomed to the Methadone, and you become stabilized completely, this will go away or diminish for most people (though there are some who say they feel euphoria/slightly high every single day after taking their Methadone).
And yes, the blockade effect due to stronger binding affinity is only true with Buprenorphine. Methadone is probably similar to Morphine in its binding affinity to the mu receptors. If you were taking maintanence doses of oral Morphine at 500mg a day, trying to shoot 2 or 3 bags of heroin in a shot isn't going to get you off; the cross-tolerance to Morphine is too great. This is why at doses of 60mg and above (for most MMT clients), it isn't worth attempting to "shoot through" your daily dose. It increases your opioid tolerance past the point where it is economical to try and get high with traditional opioid drugs of choice (Oxycodone, Heroin, etc). Though certain drugs, such as Dextromoramide (Palfium) are able to "breakthrough" even therapeutic (80mg-120mg+) doses of daily Methadone. A study was done on chronic heroin addicts in I think Sweden that tested giving oral Dextromoramide tablets to treatment resistant addicts (i.e. Methadone maintanence alone did not work for them) and it was found that a subgroup within the study was content with using 5mg-10mg Palfium tablets orally for "breakthrough cravings" rather than just quitting the MMT program or using IV heroin while on MMT. So it can be and is done. There are some links and papers out there that outline Hydromorphone as such as a drug. I can say from personal experience that IV Dilaudid certainly broke through my 105mg/day Methadone dose and provided typical strong IV opioid effects (though I'm unaware of what dosage was given at the time)- while in the hospital, IV Morphine did absolutely nothing, may as well have been saline solution shots.