I also take methadone for my PN. It has a lot of advantages, especially if it can be used as your sole drug instead of taking a bunch of others. Also, it has been around a long time and so much is known about it - and since it still has a large user base, more info can and does turn up. It is not just for people with an addiction and is often a good choice for chronic pain.
Ok - with that intro, you knew there had to be another side. It is a tricky medication to prescribe properly, in part because of its length of effective action and even more so because of its long half-life. It can be all too easy to build up excessive concentrations in the hands of an inexperienced doc. I think it is extremely important to have a very knowledgeable and very seasoned practitioner doing the prescribing.
As further proof, see this thread:
Methadone
rfinney