I have two of the 6 x 12 connectible rulers. So far I am very happy with them. I put them together and use the built in guide to set up cutting my strips and sub cuts. They seem to be accurate and I love that I can easily unattach them and pack them to bring to classes but still have a 24" ruler where ever I go.
At one point I did buy the scant 1/4 inch seam guide. I have it around, but never used it. I don't even know where the instructions are anymore.