This cuts the time by half, although once you learn how to do it, railroading doesn't take that much extra time. Some folks say that not railroading the bottom leg makes a noticeable difference because coverage is substantially reduced. And you don't have to railroad every piece. Since it adds time to your work, you may want to railroad only on a piece destined for a competition or something you hope will become a family heirloom. Those who stitch in competitions railroad all the time.
Judges can tell the difference.
And if you're doing satin stitch or bargello or some other stitch which has long stitches, your work will definiately be better if you railroad. I also think railroading helps duplicate stitch work.