As Dusk pointed out above, there is a difference between polyamory and polygamy.
Also, it should be pointed out that polygamy is not practised within the mainstream Mormon faith. It has actually been banned by the mainstream church and is now practised only within the branch of the Mormon church known as the FLDS (that is, the Fundamentalist Church of Latter Day Saints.) Polygamy *was* a defining characteristic of the early Mormon church, but it was abandoned in 1890 and a policy of excommunication was instituted in 1904 for those members found to be practising polygamy.
Now that that's out of the way: I don't believe that polygamy, as it is practised within the fundamentalist Mormon faith, is a good thing. The women (and all too often, teenage girls) who are involved are raised in a society in which they are taught that their only way to salvation is to submit themselves to marriages with much older men. They have no say in the matter (as I mentioned before, they believe that their eternal salvation is dependent upon their acquiescence to these marriages.)
Several high-profile Mormom polygamists have been convicted of sexual crimes against the women and girls they forced into these marriages (Warren Jeffs is arguably the most famous example.)
I know this is a highly sensitive topic, but I honestly believe that polygamy as it is practised within the fundamentalist Mormon church is something that should be punished to the fullest extent of the law.
As to the Mormon faith in general: well, that's kind of where your question falls a bit short, in my humble opinion. As I've already pointed out, polygamy's not a policy that is embraced by the majority of Mormons; it's just that the stories we hear about polygamy in the media have led most people to equate all Mormonism with polygamy -- and that couldn't be further from the truth. All the Mormons I know are members of the mainstream church, and none of them believe that polygamy is okay.
You really can't paint all Mormons with the same brush. I know you probably didn't mean to, but you can't just ask "Did the Mormons have it right?" without pointing out the fact that not all Mormons agree with polygamy.