I use the 45 mm Martelli rotary cutter and love it. When I helped out at my LQS I always took my own rotary cutter because I thought it gave me more control than a regular 'stick' cutter. There is a learning curve. The first time I attempted to cut fabric I took off to the right -- I can't explain why, I just always caution people new to the rotary cutter to practice on some scrap first and try it a couple of times. We didn't learn to use our stick cutters with just one pass.