I made my first quilt in 2000, then stopped until 2010. I stitched in the ditch on that quilt and have to say am pleased when I look at it but I used monofilament. I just finished a quilt (my 2nd full finish since coming back to quilting) and stitched in most ditches, then did a pattern on the outer border.
I found that using a well matched thread hid most of the imperfections. And I went slowly.