Anna does well to divide the question into two.

Is it a word worthy of notice, collection, definition and recordation? Sure. That is a democratic process whereby, if enough folks use it, it is thereby worthy.

Is it a word worthy of use? That is a totally personal question, akin to a debate about dark chocolate versus milk chocolate, scotch versus bourbon, margerine versus butter.

While my conclusion is that I would never use the word "yupster", that conclusion is worth no more than my preference of fresh squeezed lemon juice over the bottled stuff or of 100% cotton shirts over the ones with synthetic fibre.