My experience has been different than some above. I own the Amana RC-2250 (1 1/2") and the RC-2257 (2 1/2") and they both work great, but the smaller with the 2+2 design tends to plug when planing some stringy woods. I received one of the Onsrud 1 1/4" surfacers with a bit kit on my first machine, but one little 4' by 6' slab of Ipe and it was gone!
If you seldom surface there is little benefit to these insert bits, but if you cut a lot with vacuum and surface a number of times per day, they are invaluable and much lower cost than the brazed styles. YMMV