I started it around, errr... week 15 or 16?

Mostly to address insomnia though, instead of as an active "review".
I used HypnoBabies for my last birth (VBAC!) and spaced the program out so I spent two weeks on each lesson for a total of ten weeks or active lessons followed by just a few weeks of review. I figured this time I'd just listen to the first 1-2 lessons for a full month each and then go to a two week/lesson format so that again I'd have just a few weeks of review and all that "insomnia busting" to boot!
I lost the workbooks some time in the last two years but that's ok (for me, since I don't need the consumer stuff, dh isn't involved in the hypno scripts, and I know the finger drop/center switch steps already). Now that I'm at 30 weeks I'm being a bit more active... I've added finger drops to my daily prenatal routine (that includes the BAKS basics from the Tupler Technique program, a belly dance routine that takes 20 minutes, and my kegels) and have been listening to the sessions in a more active manner at least 1-2 times (sitting on the birth ball) as well as putting them on while in bed.
Personally, I found that my hypnobabies birth wasn't discomfort free, but I would describe it as pain free. In the end, I combined hypnobabies with a mantra ("just pressure, just pressure, just pressure") during the birth but didn't do anything special for pushing... this time I'm going to remind dh and my doula to put on the pushing script when it's time.