Chronic methadone usage has a number of problems associated with it, the ones I am most familiar with (From my experience working with D&A specialists) is poor teeth - easily chipped and broken, cavities etc (? related to bone mineral density changes? I am not entirely sure) as well as the significant hassle of going to a methadone clinic and having to deal with the social crowd and second hand drug market that usually exists just outside a hospital dispensary (In aust many pharmacies don't dispense methadone because of the crowd they think it attracts, and those that do charge for it, which can be a couple hundred a week, vs. free from a govt-provided system) However I did meet some people during my time at the methadone clinic that had what you are saying - a steady job, etc - but if you have a job and have to be at a clinic every day, which opens only from 8-1, and only serves 1 at a time, you better have an understanding boss...

with regard to 2, I don't know about methadone withdrawal being worse than heroin; worse here is perhaps relative; you are exactly spot-on regarding the aspects of both of them in terms of length - heroin withdrawal only lasts around a week, and incredibly you can't die from it, although it may feel like you will! - as an aside, the only drug you can withdraw from that can kill you is Alcohol (Delirium Tremens causing convulsions and death)

-- EDIT -- This image http://img546.imageshack.us/img546/9791/422a.jpg shows the biochemical effect of opiate withdrawal. This image shows enzyme activity levels in a specific part of the brain associated with perception of pain - Pain relief is correlated with the initial decrease in cAMP formation. However within a short period AC increases leading to cAMP returning to normal levels, and thus the return of pain; amplified by sudden withdrawal of the opiate - now AC acts uninhibited, there is a massive increase in cAMP and thus the 'pain' of withdrawal is experienced as physical pain, as real as being cut open