Another article says that another drawback to early s/n is the lack of gender specific characterisitics.
See this link for the entire article:
http://www.labbies.com/neuter.htm
Here is an excerpt:
LACK OF GENDER CHARACTERISTICS ATTRIBUTED TO EARLY NEUTERING. Reproductive hormones such as estrogen in the female and testosterone in the male are also responsible for producing feminine and masculine traits, respectively. Early neutering which removes the source of production of these hormones prior to complete physical development and maturity of a dog results in individuals which may appear neither masculine nor feminine. Postponing neutering for 2-3 years in a male or allowing a female to go through one estrus cycle allows for development of gender characteristics.