I use this punch constantly. It is one of two that I never put away because I may need them again. I would do that with any circle punch, but I got this one first. It is really easy to use and I can punch out a bunch of circles really quickly. I also have the medium, but will also be getting the extra large circle and some squares (when they are released). They just have endless uses.
I have noticed imperfect circles with lighter paper and it just won't punch thin handmade papers or tissue paper, but that is such a slight issue for me. A little imperfection is not a problem at all.
Edit (July 5, 2010): While I was able to use this punch many many times, when it broke it was not at all fixable. I may replace mine in the future, but I'm not going to right away. They used a plastic piece where a metal piece would have worked better. That change would have prevented it from breaking. I still recommend this entire line on punches, but they cannot handle heavy cardstock and they don't work correctly on light papers and handmade papers. Only use them on regular weight papers.