Pygeum and saw palmetto definitely have benefits for those suffering from an enlarged prostate. But I don't think that supplements can replace proper treatment.
I do take saw palmetto, but for general prostate health and to reduce the likelihood of prostate enlargement. I had prostate enlargement a few years ago and it was treated with medications. My doctor told me to buy saw palmetto for prevention. I would not try to treat an enlarged prostate with just saw palmetto however.
Also, these herbs are generally safe but they can cause side effects. One side effect I'm experiencing is sore nipples. It's an odd side effect but I know it's due to saw palmetto.