Lurking on these forums shows a lot of other people having major issues and not many seem to get it working.
That's because the people who are successful and NOT having "major issues" don't go on forums and post thread after thread about how wonderful and smooth things are going. The reason it looks like "not many" people seem to "get it working" is because the sample population you're looking at here is skewed.
I would venture that there are just as many if not more monogamous people who are having "major issues" in their relationships, they just don't go on a forum for non-monogamous people and complain about it.
In my experience and the experience of those I have read about who are having what could be described as "successful" non-monogamous/poly relationships, it comes down to CHOOSING THE RIGHT PARTNER(s). This is so crucial in so many ways, I don't even have the patience to explain it properly. Indeed, it is easier said than done. But I have noticed that most people get involved in a relationship, THEN get to know what kind of person their partner is. Sometimes, we get lucky and actually end up with someone we are very compatible with (this is what happened with me and my Spouse). More often than not, folks meet through friends, work, or common interest, become attracted, hang out, have sex, fall in love, move in together, and allow their lives to become intertwined logistically, emotionally, and financially, before realizing that there are some fundamental incompatibilities and stumbling blocks that threaten the long-term viability of the relationship (monogamy vs. non-monogamy is only one example of this. Another common example is whether to have children. Often, one partner is "on the fence" about having children and the other feels strongly about it one way or another. This can cause problems down the road, often after kids are in the picture and it's too late to turn back and try the other way).
To base one's life choices on the experiences of people one reads about on a message board is a bit shallow and dismissive to me, as it suggests that one does not really know oneself and should probably not be in a serious, committed relationship with ANYONE, monogamous or otherwise, without doing some serious introspective contemplation about what one wants out of life, and EXPERIENCING things for oneself. I don't believe that looking at what other people do in their relationships and the results they achieve, and then saying "that proves that X is fundamentally flawed so therefore the opposite-of-X must be the "right" paradigm" is the way to go about living one's life.
But that's just me, and I understand that for a lot of people, it's easier to just follow the mainstream life-script because it's already mapped out and there is a simple formula that can be followed which will lead to fairly predictable outcome.