Love my Martelli rotating mat! And the JT strip cutters are great! I have 8 of them. Not a fan of the Creative Grid ones because mine is not wide enough to cut a double folded WOF completely. I have heard that they have corrected this problem.
What makes JT work so well for me? I purchased metal spring clips at the hardware store and clip the ruler to my cutting mat after placement and before cutting. Now, with experience, I can cut accurately using only one clip on the cutting end and my gloved hand on the other end as I cut. Never a problem. I might also add that my glove is a Coast Guard glove inherited from my son that cannot be penetrated by anything sharp. Great grips and uber safe!
BTW, I cut everything for a charity bee and my tools have to be as problem free and reliable as I can make them. This is what works for me.