How do you stitch the grids? Is it just tacking every 10 squares in a contrasting colour? And do you unpick it after the x-stitch is done, or is it just sewn over? I ask because (as you say) it would be incredibly helpful in counted x-stitch, but the patterns I'm currently working on are all using very tiny stitches (which would make it difficult to unpick a grid once I'd sewn over it), and also don't have backgrounds, so parts of the grid would remain visible once the pattern was finished.

It's my mum's 60th birthday soon and I'm going to make her an embroidery pattern based on this picture, or rather a section of it. Actually I'd better start working on that soon, as I think it might end up taking a while...