I've got the rotary cutters, mats, rotating mat, quilting rings for dsm fmq and the binding system. Each product is so well engineered and of such quality that it's a pleasure to use! Because they are expensive (and they ARE), I wait for sales or find them at a quilt show and buy with special pricing.
The only product of theirs that I gave away was the long, wide ruler that won't slip. It's opaque. I can't see what I'm doing and that never worked for me.
Of all their products, my favorite is the rotating mat...it's sturdy and turns on ball bearings. The small Fiskars rotating mat that I bought for portability is just a shabby wobble by comparison. Buy Martelli!