Have I ever been in a polyamorous relationship? Yes, I have a hodgepodge of a family right now, with essentially two husbands, a relationship with one of my husband's submissives, and another submissive that I'd like to see gone because of her age.
In reading through prior responses, I'm surprised at how many people equate having a polyamorous relationship with having sex with another person outside of marriage. Or how many people say that polyamory isn't "serious". I think a lot of people are confusing polyamory with swinging.
Relationships developed through polyamory are just like relationships developed any other way... you meet someone, you're attracted, you flirt, you go on a date, you wonder if she'll ever call you back, you get giddy when she does. You wear a stupid, happy expression that makes your husband chuckle and start unpacking double ended dildos to have them handy, just in case. Your life becomes a hectic whirlwind of time management nightmares.... ugh. You start feeling closed in by a house of 3000 sq feet and start dreaming of more bedrooms and an even bigger bed.
Polyamory is not swinging. There is nothing wrong with swinging. It's super fun, but short term and commitment free. Just good old sex with other partners. NOT polyamory.
Polyamory is having multiple loves. Multiple relationships. Multiple people in your life on a consistent basis. You have personalities to juggle, jealousies to overcome, and never, ever enough time for everyone. Ever. Scheduling helps, and being flexible about the scheduling helps even more. With a positive attitude and a lot of patience, polyamory can be a very rewarding choice for many families.