I'm really tempted to get another one for use with my laptop, but I'm currently using a left-handed Elecom trackball that is wireless - it's fine, but not the sheer luxury of a Ploopy.
Most of the Ploopy trackballs are designed for fingering(!). The one shown in the article looks to me like the Adept model which I have too and is not a thumb-designed one.
(My Elecom left-handed wireless trackball on the other hand is a thumb-oriented one. They take more getting used to as thumbs aren't quite as dextrous)