It sure works (for most men) in causing erections. But it just never feels natural.
For me (Gary from Philadelphia, Pennsylvania) it causes unbearable headaches, and weak orgasms.
I have now discovered a better, natural alternative: black ginger, kaempferia parviflora by scientific name.
Its origin is in Thailand, where it is called krachai dam, or krachai dum. You can check the Thai writing via the Wikipedia entry.
I said that I now discovered...? Obviously it is not me who discovered the amazing effect of this herbal which basically restores erectile function in men who have suffered in this department.
I discovered it now, or better recently. But it has been known as a sex booster in Thailand for hundreds of years.
And then, there is a large body of scientific research into kaempferia parviflora. Practically all clinical trials confirmed that it works like sildenafil citrate, albeit more gentle.
I suggest you visit scholar.google.com to see studies.
I have now started retailing kaempferia parviflora on this domain, which actually I rented.
I obtain my krachai dam from Sumatra Pasak Bumi (website: tongkatali.org), and I sell cheaper then they do.