Early neutering is more likely to prevent objectionable behaviors than when done at a later age.
This has not borne out. Neutering at any age is associated with the same statistics as listed above.
Kittens neutered early will be stunted or small.
This is not true, though early neutered kittens will not develop the more masculine appearance described above.
Early neutered kittens will have a narrowed urethra that will predispose them to blockage with feline lower urinary tract disease.
Early neutering does not seem to be a significant factor in this syndrome.
Some clinics support early neutering but prefer that kittens weigh at least 3 lbs so that the tissues are not too difficult to manipulate.