I just got mine a few days ago - which completes my troika of Brynes Machines. Both Byrnes sanders are more for fine tuning pieces rather than heavy stock removal. The compound miter on the disk sander is very, very useful for creating certain effects.
The thickness sander is excellent for getting uniform thickness on small pieces, which is an absolute must for complicated segmentations. It's also great for leveling off veneer strips that the Brynes Saw doesn't quite nail to my satisfaction. The Byrnes Saw is very powerful and brittle acrylics get eaten up between the blade and the rip fence if you try to get too thin. With the thickness sander, I successfully achieved a .008 thickness on a piece of black onyx that the saw destroys past .03 thickness. (I used the method where you glue the strip at each end to a piece of wood, run it through carefully, then debond it.) A piece of paper is .004 thickness and I think it could get to that, if needed.
Another great use for this sander is the creation of custom "pickguard" laminates, and also for getting that last 5% of accuracy in squaring up blanks for drilling on the lathe.
It's a worthy addition.