I have Olfa cutters in 60/45/28mm -I've never had a problem with them at all...
That being said, I bought a Martelli cutter at the Houston festival last November and I absolutely LOVE it.
They make two entirely different cutters for left and right handers (not just a matter of swapping the blade around the handle.)
I'm a lefty!
Joann's has them on their website sale priced at $17.99 (reg $29.99) definitely the time to buy if you are interested!