Ive tried the HAPP 3" illuminated trackball - 3 of them - and all of them have an issue whereby if the ball is lit, but not in use, one side of it gets hot and then the ball sicks. Its a total pain in the arse - not to mention the outdated mounting plate and odd shaped hole you need to cut into your CP.
That said, I have the smaller - none illuminated - one in a little bartop and its great. Except for the mounting plate which is a monstrosity. And the smaller stupid hole. Obviously you can route out the hole and hide the plate. What a fuss.
I also have the ultimarc one. Works great, no stupid mounting plate, round hole. Wish Id put one of those in my other machines.
Mark