any longtermmethadone users switched to subs?

[Santa]

Swim has used heroine (IV) and methadone for over 23 years. The last 6 years she only used methadone (30 mgs). For several reasons she wants to switch to subutex now.
She has heard positive as well as negative stories about making the switch from methadone to subs but has hardly read posts from longterm methadone users (using about 15+ years) who switched to subs.
So if you are one of them long-time-done-heads who actually swapped it for subs: what's your experience? From what dose did you jump? How painful was it? And do you consider it an improvement or not? Swim would really like to hear your stories before making switch herself. Thanks.