I will not answer your question, because, I am not sure what you classify as negative and if you are posing your question as an individual or as a anti-Obama person. I will tell you the benefits.
1. Cannot be turned down for age.
2. Policies will all have to cover essential benefits, so some company does not give a half-baked policy to its employees.
3. Tax credits are going to be available to lower the price for people on lower incomes.
4. If all insurance meet the same essential requirements, health care will be more equal.
5. If everyone is required to buy insurance, the pool of people paying premiums will increase and premiums may decrease or at least stay constant.
6. The need for people to wait more than 24 hours in the emergency room of a charity hospital will be eliminated, since there will be more options available to them.
I really cannot name 10 reasons. But 10 is only an arbitrary number. Everything and every action does not have nor need 10 reasons to justify its existence.