SAM-e was mentioned in Freddd's discussion about his protocol, not in Rich's as far as I can remember. It's the "active" form of methionine if you will, and it's typically low in people with methylation issues.
If you're already taking reduced folate and active B12, SAM-e is one extra element to experiment with, starting at a low dose of say 100-200mg.
It can be useful to deal with histamine issues for under-methylators, helps supporting neurotransmitters balance, supports glutathione dependent enzymes, helps maintaining a healthy connective tissue.
I've been on a and off of it for some time and I haven't seen or felt major differences. Other people have found it very helpful.
At dosages of 100-400mg it's very safe (don't take without adequate methyl supplements or it could raise your homocysteine)
cheers