I use both mat and ruler for measuring. Sort of depends on what I'm cutting and how it needs to be approached. It's funny how much of this stuff you do without even thinking about it until someone asks a question. There was a thread a couple of days ago about ripping vs. cutting in fabric shops and I was surprised how many people said they preferred to have a fabric purchase cut. I always prefer to have it torn; saves me having to waste fabric establishing a straight edge.