I make no apology for this, but I am a complete sucker when it comes to this type of card. The clear plastic cards that Fleer, in the guise of Skybox EX, foist upon collectors firstly in 1999, and then again and again for the next few years, are the sort of cards I like to have in my collection. Long lasting, strong and transparent.
Although I can see why collectors may baulk.
In Australia they have plastic money, yes plastic notes of various denominations,made I am to led to believe of recycled supermarket carrier bags. When you see and feel this money it just isn't right. Real money should be metal or paper, credit cards are plastic. So it may be roughly the same thing with baseball cards. They should be made of cardboard. Vary the thickness, add a piece of bat or clothing, draw on it if you like (but don't put stickers) but never, NEVER make them from plastic.
Whatever your take is on this type of card, they have to be admired for innovation and trying 'something different'. Is there any harm in that? Some collectors spend a fortune making their cards plastic anyway through the grading process. As I have heard it put recently, the card collecting hobby is for enjoyment. Although I must mention the 2003 version of EX tried a little too hard to be different. The background is very sparkly, too sparkly like lip gloss. If you have young daughters you will know what I am talking about. If not, try to get a hold of some of these cards to get feel for them yourself. I like shiny cards but even this is too much for me. 
