I started my first TB with a USB pro version of that. (Not on a CP, though; just let it as is.) (Not sure about the serial/PS2 connection version you're pointing to, though).
It's great, with one major problem.

Nothing is holding the ball in, and it pops of the rollers if you hit it at too low an angle from the side. And since it's a high sitting ball, it's easy to hit the sides. (I have the same problem with happs high ball.) If your way of interfacing with the TB is just the on the top, or you mount it so less of the ball is showing, you might not get this problem.
Personally, I like any of the arcade 3" TBs (happs, happs high lip/GT, betson GT, or wico) with the exception of happs high ball.
I still use my expert mouse every day on my desktop, though. I even sometimes still play mame with the kensington TB if I want a quick play on my desktop, and am too lazy to pull out (and make room for) my TB CP.
It's one of the highest end PC trackballs you can get, IMO. Roll, spin, speed: excellent.