Polyester gets a bad rap.
When I was growing up in the 80s, "polyester" was like a swear word. We associated it with the fashion excesses of the 1970s, all loud colors, garish prints and extreme silhouettes.
Then a couple of things happened. By the 90s, the 70s were cool again, at least among certain alternative/hipster circles. When I was in high school, I got a hand-me-down* polyester polo shirt from my older sister that caused me to rethink my hatred of the fabric.
The shirt was bright yellow, with a criss-cross design in green, pink and purple. It fit me well, and I soon realized it was super comfy. Unlike cotton knits, the fabric hung away from my body and didn't cling. It never got wrinkly, and even after wearing it every week for a year (not to mention the years of wear it had gone through before me), the colors were as bright and clear as ever.
Now, of course, polyester is commonplace, and the fabric has come a long way from the scratchy double knits of the 1970s. But some vintage pieces - like this one - still stand the test of time.
*Actually, I just borrowed it and never returned it. Its return was brokered eventually, as part of a complex prisoners' exchange of sorts in which we both fessed up to clothes we had taken from each other over the years.