patricej

that is a pretty nifty looking accessory.
pricey, but nifty.

one thing to consider, though, in regard to stitch-in-the-ditch feet in general ...
they can actually make it more difficult to keep the stitch line straight and properly positioned in relation to the "ditch" when quilting over nested seams that have been pressed to one side or another. unless you pay very close attention, slow down as you approach those intersections, then either shift the quilt ever-so-slightly or adjust the needle position, the line of stitching will alternate between being in/near the ditch and being near/on top and visible.

i only use a ditch foot when i have pressed my seams open.
otherwise, i use an open toe walking foot so i can keep a better eye on those pesky side-pressed intersections.

of course ... my quilting skills are quite "iffy" whether i'm doing straight/curved lines or free-motion.
a quilter who's more skilled than i am might have a different perspective and offer better advice.

going back to that accessory set, though, i could easily see myself falling in love with the other piece - the adjustable guide. it looks like it would be a lot easier to use than the little bars that often come with walking feet.