You can quilt with the decorative stitches. It takes more thread, and they are slower to sew out. It's a good idea to try a few on a practice sandwich to see what they look like.
I helped my sister do one quilt with a decorative stitch. The stitch was really pretty, but it took *forever* to finish! It just took a long time to sew a line.
My favorite decorative stitch for quilting is actually the serpentine stitch. It looks like a big S repeated over and over. It is a very forgiving stitch, easy to use on top of seam lines (for example), and sews out fast compared to say a feather stitch.
With decorative stitches, you leave the feed dogs up and simply adjust stitch length and stitch width to your liking.