Israel is not happy. Many Arab countries are unhappy. They can simply declare they do not accept the ICC's jurisdiction - if the crime is committed on their territory or by one of their nationals. This is a serious flaw in the treaty. The time frame for establishing the treaty also permits current atrocities to go unpunished.
Crimes can continue unabated until the treaty becomes law.
And, under pressure from the Arab states, chemical and biological weapons were not mentioned in the final treaty. The agreement does include the crime of aggression, but doesn't define it. It will do that at a later date. The Court was championed by the Non-Aligned Movement, but did not include India's demand for the use of nuclear weapons to be defined as a war crime. But, ratification is still a long ways off.