I was is such a hurry to start an adorable baby hoodie, that I missed the instruction for casting on a provisional cast on! I'm over half way done with it -- do I pull it apart? Pick up the stitches from the right side, hood, left side then just pick up the bottom stitches? Help!
If you are using a relatively thin yarn, picking up stitches from your cast-on won't make an uncomfortable ridge. You could turn this into a "design feature" by doing your pick-up so that the cast-on line is on the outside. Overcast it with contrasting yarn! Go wild! If you are using a thicker yarn, you might want to unpick your cast-on.
I'd say pick up and leave the cast on for anything thinner than worsted. Worsted and thicker I'd try to unpick the cast on, I hope you aren't using a bulky mohair yarn ;)