Ok, so I get the polyester hate on here. It makes you sweaty, often it doesn't feel nice, and 80% of the crap, ruffly blousons available in high street shops are made from it.
BUT. But...
I do have some lovely, vintage or vintage-repro dresses in polyester and the cuts are beautiful, the colours remain bright and the fabrics wash REALLY well. My favourite is a circa 1980s ww2 style navy blue tea dress with a cinched waist.
We also don't talk about how some blended fabrics (polycotton etc) combine the best of both worlds - the warmth of natural fibers and the hard-wearing qualities of manmade.
I'm interested to know about the polyester items you own and love (although fair play if MNers don't want to share!)