Mommabear62,
I like my Martelli 45mm for most things,also have the Olfa 60mm,45mm and 28mm and a 45mm Fiskars with the grey handle; not the new one being sold now. I find that the blade release is too hard to operate with an arthritic thumb.
I use the 60mm when I'm cutting layered blocks like "Layer 'em Up" by Sharyn Craig.
Its possible to get a bad blade that's brand new.