@funkyqueen was given rituximab at OMI - I think it helped her initially and then stopped helping. (
http://forums.phoenixrising.me/index.php?threads/my-rituximab-experience-for-me.38239/)
Actually, I think what happened was she unable to continue treatment where she lives, the above thread is rather long and goes into more detail.
@Gingergrrl also has been to OMI. She is very ill, though she may not have ME/CFS. I believe she's currently taking a break from the board but hopefully will return and you could ask her about her experience.
I'd consider myself medium sick - not bedridden, and not extreme POTS or OI, but my life is seriously disrupted - I can't work and am quite limited in my daily activities. I went to OMI, they did a lot of testing but were unable to help me.
So I think it's a mixed bag, depending on your symptoms, etc.