
We have been using this detergent for over a year now and are happy with how well it works. I have gotten grass stains, grease, and blood out with it, with no pre-treating. The only thing I wasn't able to get out was some salad dressing. For Baby spit I pre-treat with a tablespoon of this detergent dissolved in a quart of cold water. Soak for an hour and then wash as normal.
It also rinses very cleanly and we have not had any buildup on the diapers after roughly 60 washings. So we haven't had to strip the diapers. If we do, I will let you know how long it took.
My wife and I have sensitive skin and have not had any irritation. I would not call it hypo-allergenic by any means, just an anecdote that it works for us and may work for you.
Now then, how to make it:
My Equipment (with local prices):
Washing Soda ($1.50/box)
Borax ($3/box)
Fels-Naptha Soap ($1/bar)
Microplane Grater (~$12)
You will use 1 bar of soap, 2 1/4 cups of Washing Soda, and 1 ½ cups of Borax per batch.
Grate the Fels-Naptha soap on the smallest holes on your grater. I prefer a Microplane, but I started making this soap using a generic $4 box grater. Both work well, but the Microplane makes a quicker job of it.
Once you grate the soap, mix it and the other ingredients together in a container. I use a 1 gallon plastic jug that used to hold biscotti. Now it holds three batches of laundry soap with enough room to shake it and mix the ingredients.

I use 1 Tablespoon of detergent per size of the load (1Tbs for a small load, 2 for a medium, 3 for a large, 4 for an extra large). We have a top loading washer, so I don't know how it would do with a front load or HE washer directly. From folks I know who tried this recipe, it worked fine in an HE front loader as it doesn't foam up.
But, the last bit of good news, the cost. A box of Arm and Hammer Super Washing Soda is ~8 cups. The 20 Mule Team Borax is around ~10 cups. So, one batch yields approximately 108 Tablespoons of detergent, and I can get 36 large loads of detergent for about $1.90, or $.06 a load. Compare that to a 240 load pack of Tide powder at $53.70, or $0.23/wash. The savings add up quickly and the time requirements are low. I can make enough soap to last us several months in 30 minutes.