Gridding seems to be one of those topics that cross stitchers have strong opinions about. Every time someone asks on one of the discussion lists, it sparks nasty comments from people who think it's a waste of time.
I grid almost everything these days. I can stitch without the lines, usually, but that extra safety net keeps me from abandoning projects.
I lost almost an hour to this project. The red stitches weren't lining up with the blue letters correctly, no matter how many times I counted. Finally, I realized that my "W" is misshapen. Everything else I've done lines up with the mistake in that first letter. Which means I can re-stitch just the "W" and keep the rest of my progress, but it took lots of counting and frogging stitches to get to that point.
If my fabric was gridded, I would have found the problem much sooner.