Even when I did have a design wall right next to my sewing machine, it is absolutely amazing how many times I sewed the blocks together on the wrong side or some issue. I think a lot of it is just the style I quilt, it wouldn't make much difference if all my blocks were the same design and same fabrics, but I'm usually alternating blocks or trying to move color through my scraps or some other reason I want to be precise in my layout.
As it is, I have to do my layout on my queen sized bed as my largest work surface, which makes it rather fun to layout a queen sized or larger project!
But with design walls too, I think they work best with consistency, like starting in the top left corner or whatever, helps to keep those blocks from flipping but not as well for me as my labels!