The US is behind much of the world in having plastic currency. Ours is still printed on a cotton/linen blend. They only way we can pay with "plastic" in the US is by using a credit card (or charge card or debit card) and that doesn't appear to be changing anytime soon. Speaking just for myself, I really don't care either way whether our currency is printed on plastic or not - it's just not something that I feel strongly about.
A new proposal in India is now taking the idea of plastic currency further however and looking at replacing metal coins with plastic ones. This strikes me as odd for a number of reasons. While polymer currency id more durable than paper currency, metal coins are already quite durable, lasting in some cases hundreds and thousands of years. Plastic coins just aren't going to match that. And since do-it-yourself injection molding already exists, plastic coins could be cheaply counterfeited. While counterfeiting metal coins can also be done, there is little incentive as the margins would be pretty limited. Plastic coins will weigh less than the metals ones they replace, which can be viewed positively for anyone that has to transport a large amount of them, but all the vending machines would have to be retrofitted to compensate for their radically different electronic signature. But perhaps most importantly, metals coins have some romantic aspects to them that plastic won't match. The sound that they make clinking together is strongly associated with wealth. Imagine the 100th anniversary remake of Pink Floyd's "Money" using plastic coins in the intro instead of metal.
This is a great example where plastics shouldn't replace metal.