I just think they're neat. I hate traditional mice and trackpads. The trackpoint nipple thingy they have got on thinkpads is my favorite pointing device but that is not available on most keyboards, but it should be. Trackballs are my second favorite
been using a kensington one for a couple of years and I don't think i will be able to use a mouse ever again. While this model is not great and it could use some improvements. The whole idea of a trackball is really comfortable
that said, I lost the original ball and it has been incredibly hard to find a proper replacement. we have tried many different ones and they all have downsides that make the experience not great but still better than a mouse