I’ve used hundreds.. I don’t need them, but I like to use them now and then.
A half tablet or a bite out of a tablet will be enough for most first time users, but it depends on the person’s health etc.
Side effects for the first few tablets include rolling eyes, blurred vision, and a stuffed up nose (it seems there are PDE5 recepters in the penis, nose and elsewhere). Orgasm may also be blunted. These side effects dissipate with use. De-sensitization to the drug builds up very quickly.
I personally think nothing beats the rigidity of Yohimbe, and that can be obtained easily on ebay etc. Side effects with yohimbe though include not being able to sleep for 24 hours or so…