Hey there flooringmaster, welcome to the forum!
The EZ-Shear cuts all laminate flooring products under 9/16" thick (with the exception of the now defunct Wilsonart Estate high pressure laminate). It will also cut solid pine or cedar (as in siding), most engineered hardwoods, and works great on fibercement products. (Bullet Tools has a 'cut guide'
here with more information).
You will sometimes find that a burr forms on the edge of your blade after a dozen cuts or so (I presume this is what you noticed as "dulling"
. This is normal and can be corrected using the "little stone" you noticed; it's the hone stone which came with your shear. Press the stone firmly against the
flat side of the blade (the stone should be above the black plastic table) and slide it back and forth a few times. This will true up the edge of your blade and improve your cut quality. If you maintain the blade with the honestone, it'll probably last you 5,000 to 10,000 cuts on laminate or fibercement!
You should also lubricate the machine periodically. Wipe off the old grease on the "Pins" (the vertical shafts with the springs on them) and the plastic bearings and apply new lube (the instruction manual recommends 10W-30, and some guys spray it with WD-40, but I've found good old lithium grease to last longer and run smoother). If it starts squeaking that's a clue that it needs grease/oil again.
"Why is the only time I'm right have to be when I realize I'm wrong?"
~Nathan the Stout