I went from natural to twists to locs. I had been rocking twists for at least a year, so it wasn't a big deal. I have incredibly kinky hair, so it didn't take long for them to twist at all. It was pretty easy actually. The only thing I would suggest is if you're not used to doing twist or sloppy like me, think about getting someone to do the initial twists so they'll be even and consistent.
Mine grew to shoulder length and then I got bored. I was able to cut them to about two inches and unravel. In retrospect I may have not had to cut that much.
A coworker told me coils are a better transition, but YMMV.