Things to look at when buying rulers for doing ruler work is whether or not they are the correct thickness for your machine and whether or not they have enough markings to enable you to use them without having to do extensive marking. I really like the Westalee rulers because of their extensive markings and also the ones that Handiquilter makes for the same reason. I also tend to use the same few rulers most of the time- a short straight ruler with lots of markings, a gentle curve with lots of markings for lining it up, a couple of curved rulers that are based on circles not ovals, and the Westalee Circles on Quilts rulers (perfect circles every time). I've got others that do specific designs and they're fun to use on occasion, but I find that I having the straight, gentle curve, circle curves and circles on quilts give me lots of versatility in terms of quilting designs.
Rob
Rob