I've been using the homemade laundry soap for about two years now, I love it. I have used Fels Naptha and Zote as the bar soap, we liked both but preferred the Fels Naptha as the Zote came out clumpier, perhaps it was our technique.
I'm not familiar with the brand Octagon, but I've heard you can use any detergent bar of soap. Actually, I've heard you could use ANY bar of soap, but in the more complete discussion of this at BYC, people mention issues with using any bars that are moisturizing, like body soap, Dove, Ivory....although there is a lady on their that uses Ivory all the time. Apparently there could be an oily residue on your clothes from moisturizing bars? I'm not speaking from personal experience.
Why did you not want to use Fels Naptha or Zote? Where did you hear that Fels Naptha is not so good? I would disagree, I love the stuff. Tell me why you don't like it, I'm curious.
The way I understand it, aging soap just makes it harder, which isn't a problem if you are making the liquid laundry recipe because you are going to grate and melt the soap anyway. Perhaps someone using the dry recipe has imput on that, but I've never made that one.
I'd say the only negative thing I can possibly come up with to say about homemade laundry detergent is that your colors can get dingy after awhile, you need to use bleach occasionally on your whites and make sure to wash same colors together.
Edited to reflect I've found and read the other thread, so I understand why this was brought up here now.