I have been using the Festool sanders for about 3 years now and could not be happier. Yes the stuff is pricey however you get what you pay for.
For those of you that are familiar with the red Ruben sand paper you probably know that it is a cloth backed paper that I have have found to outlast the typical vendor branded paper.
Several weeks ago I was doing a lot of sanding, in particular, sanding a lot of glue squeeze out around those exposed Domino tennons on that large group of drawers I built. Because the tennons are proud of the surface when glued in place it is way difficult to wipe of the excess glue. Anyway I was replacing the red Ruben sand paper with each of the drawers. It was loading up with the excess glue. I had 23 on the first run.
Enter into the equation the Festool "Crystal" sand paper. This sand paper outlasted the Ruben sand paper 10 to 1 and excess glue squeeze did not load the paper at all.
SO if you are looking for an aggressive paper that is not affected by excess glue and lasts a very long time, consider the Festool Crystal paper. It's finest grit is 120.