It has never occurred to me not to backstitch with my walking foot - do it all the time. Decor stitches too and it just performs beautifully.
Sometimes when straight stitching, instead of doing a backstitch, I ever so gently hold back on the fabric as it enters the stitch area, causing two or three stitches to be made in the same or nearly the same place. Has the same effect as a locking stitch without the normal "buildup" from the programmed six-stitch lock. I've never had a seam let go that has been secured like this, nor has my fabric ever stretched from the very gentle "hold-back."
BTW I use a Kenmore machine and the walking foot available through Sears. I've had it for years and never had a problem with it. I do keep it cleaned and occasionally oiled on its moving parts.