I tried something called "Max Viril", which is sold as a herbal supplement. However, it appears that it's really just ordinary Viagra with some benign herbs thrown in so they can call it a 'supplement'. Later research seemed to indicate it may actually contain three times the normal dose of Viagra - this I researched after experiencing the side effects.
My situation is that I can get an erection on my own so there's nothing physically wrong, but with other guys I seldom get one - this is because most encounters with guys have been disappointing, in that's all about them, or they want to do things I'm not into. So when I meet up with a guy it's now pretty much entrenched in my mind that it isn't going to end well, and I won't get hard. For me, sexual stimulation is more of a mental thing - I have an extremely insensitive penis, possibly due to how I was circumcised.
Anyway, how well did it work? Well, it seemed to work after about half an hour, and yes it did get me hard when I wouldn't have otherwise. It wasn't a rock hard erection, but better than a semi. However, I found it extremely difficult to trigger an orgasm, much more so than if I hadn't taken it. It was like the sensitivity of the penis has dropped significantly. In fact, I had gone soft again before I got to the orgasm.
Several hours later, I started to feel a bit tired, but next day I felt like absolute crap. A bit of a headache and felt really drowsy. I just wanted to fall asleep all day. The day after that I felt OK again.
Maybe a smaller dose (say one third) might be the answer. I would prefer to see a doctor to get the right amount, but in the semi rural area where I live, the chances of finding a doctor that isn't hung up about sex is pretty remote.