Did not work for me. I did it twice, at 40.5 & 41 weeks. It made me feel terrible. But I did do the at home enema which, though not comfortable, at least cleaned me out for labor.
My mw recommended both. Neither started labor for me, but I'd be willing to do the enema again before the castor oil.
I got an Asian acupressure massage, though, and the contractions started that night... It's always worth a try. Worst case is that you get a message!