This is a question I get a LOT, and I’m never really sure how to answer. Yes, homemade laundry soap is awesome. And yes, some people really love it for their diapers. At least, they do at first.
Everyone’s experiences may be different, but I personally do not recommend using homemade laundry soap on your diapers. And rather than reinvent the wheel, I’m just going to send you over to a link from Little For Now that does an awesome job of discussing the issue.
I’ll add to this that if you live in an area with hard water (so, Iowa), homemade laundry soap isn’t going to get your diapers very clean. You could just end up with soap scum on your dipes and in your washer.