I have been to Retro, but don't use my situation as an example. It helped and it didn't. I had to twist W's arm to go. I knew at the time she had been 'influenced' by someone else (OM) but I wasn't sure of the details and just thought she was confused and that this might help us sort out a positive direction.
What it did - it made me realize that ANY problem in a M can be overcome so it gave me hope and strength to persevere through the past year of pain and turmoil with her. Without Retro I don't know how I would have had the resolve to see this to the bitter end no matter what the circumstances. I might have given up a lot sooner. I still haven't totally given up, but W is now really making moves to leave and OM is still around.
What id didn't do - as far as I know it had no impact on W but later I found out she was in a heated EA with OM during this and through the first 3-4 post sessions, after which she went into a depression due to OM-withdrawl after I investigated and uncovered the affair (and exposed her to friends and family a little too soon).
If W is in an affair, the Retro experience is counter to the advice you get here. Retro is all about expressing feelings to one another and communicating, whereas if WAW is in an affair you need different tactics. In my situation Retro might have actually hurt the situation between myself and W, but I certainly got a LOT of inspiration. Who knows, maybe in back of W's mind she realizes that things could work possibly if she would decide to dump OM.
Anyway, given the presence of an OM in my situation don't use my experience as an example.
ME/XW:47 S21, D19, S15, S14 M:21 T:26 W moved 6/10 I filed 7/10 D final 4/12 remarried 8/12 W wants to R 12/10 and 4/11 but I decline