The basting stitches are hard to remove if they've been stitched over. It is very easy to remove them while quilting (I am a slow quilter and am constantly stopping to consider my next step anyway, so I don't consider it an inconvenience).
My little skein of DMC tatting thread has an 80 on the front.
It is easier to quilt the edge of your quilt if you have extra batting and backing around the outside.