I bought one for my office and my employees hated the plastic aftertaste so I switched to a small espresso machine. It's not as practical than a capsule coffee maker, but for a couple of minutes more you get a great coffee.
I've never heard of these capsules leaving a plastic aftertaste. In my experience, it does taste different (and some tea formulations just do not handle it well at all), but not like plastic.
I got the Nescafé Dolce Gusto machine and its pods. This was the first capsule machine whose pods were kinda common and available in every Walmart, and yes, the coffee got a hint of plastic like the lid used in Starbucks cups. Also, we're coffee purists in the office, so a small bad taste is enough to switch to something better: that's why I'm planning to get them pour over for their cups. Nothing beats the taste of pour over coffee.