For squaring up blocks, it sucked. Maybe because I was using it on a small-ish table. But it didn't seem very easy to use for this and the lines are harder to see than regular rulers. However, I used it to cut bigger fabric pieces tonight and it was perfect. I didn't use the lines though (the piece I was cutting was wider than 6" so I used two rulers butted up together) but the cutting part was super easy. I wish the lines were like regular rulers.
eta: I ended up using a regular ruler to square up the blocks (too bad I can't find my square-up ruler) and it was much easier so it was pretty obvious the true cut ruler wasn't going to be good for that. For me anyway.