I agree with BellaBoo - I love Creative Grids. Also try out some of the rulers that they have at different shops, see which works best for you. I used to love the ones with the yellow but now I have a hard time seeing with them. I like the non slip feature of Creative Grids, but think you need to really use or at least put it down on fabric, move it areound and see if you like it. Remember you are not just buying a ruler, but a tool that is the start of all of your projects.
Personally I have gotten the you have to use the same brand speech also, but really don't get it. An inch is an inch, and I have put ruler upon ruler and not seen any difference (at least not yet). I think the real issue is how good you can use that brand of ruler and do you read the other a little differently - like is the line thicker so maybe you don't get as good of a measurement?