I have to say, I have had nothing but good experiences with guppies. But there are a few considerations beyond just male:female ratio. I consider live plants a must, and the more the better. They create a more natural environment that I find to be less stressful. Also, more plants means more hiding places and fewer direct lines of sight for the fish. It tricks them into thinking there are fewer fish and more space.
Another consideration is stocking levels. Like many cichlids, more is better. One two males will bicker if they can see each other at all. Six males (and correspondingly, 18 females) seems to have very little aggression. I don't necessarily understand the dynamic beyond spreading aggression out, but it seems more is better.