I use soap nuts which is kind of the same concept. I love using them! No they do not remove stains very well, but if you use liners this is not a problem anyway. I never have to worry about detergent residue, allergies to detergent, or not rinsing well enough.
I do a soak first in vinegar and then add water softener to the wash cycle (I have hard water).
If you can line in sun dry great! I can't line dry so I run the occasional 90 degree wash.
I never have problems with smelly nappies but if you are worried just give your nappies a good smell as they are coming out of the wash, to find out if the eco balls worked.
Oh and I believe the occasional bio wash is recommended no matter what non-bio alternative you use to wash (incl nonbio detergent)
Let us know how you get on!