I quit Methadone cold turkey (quit because I gained 30lbms and had SEVERE secondary hyperhidrosis and did it cold tukey because the clinic planned to taper me off over 12 months and told me I'd feel "somewhat unwell" the entire year). I wasn't on a particularly high dose (60mg/day) but I was also using probably a gram of heroin a day, too and also quit that.
I felt relatively okay for about 10 days and then I was very drastically ill for 10 weeks (think acute heroin withdrawal but for 70 days).
I improved a lot after that but the PAWS never went away until I started taking morphine about 6 months later (from a doctor, I have severe chronic pain and need opioids to live). I think Methadone is worse than almost any other opioid because of the insane amount of time the withdrawal goes on for. Considering it was synthesised by the Nazi's, I shouldn't be surprised.