The recent health care act dubbed "Obamacare" in the media is actually called the Patient Protection and Affordable Care Act. It was signed into law in 2010 and was designed to make health insurance more affordable to more people and increase overall access to health care via affordable health insurance. It works through the existing heath insurance industry which is what makes it such a political target from both ends of the political spectrum. Conservatives do not like any involvement of the federal government into the health care system. Many liberal progressives who favor health care reform do not like it because it keeps the for-profit insurance company model in place instead of a single payer system administered through the government like you find in Europe.
The law was designed to be implemented in several stages over a period of time instead of all at once. Certain aspects of the law were implemented immediately after it was signed into effect. These include children being able to stay on their parent's plan until age 26 and the ending of people being denied insurance covereage due to pre-existing heath conditions. These immediate effects tended to be easy things to implement through policy changes at insurance companies. In terms of access to health care, these early changes have expanded access, particularly for younger people (with too low an income to afford insurance) and for people with chronic health issues where pre-existing conditions caused them to be denied a new insurance plan.
The full extent of the law is scheduled to go into effect at the beginning of 2014. This is when the individual and business mandates go into effect and also when the state insurance exchanges go into effect. The exchanges will allow people to buy health insurance coverage as part of a larger group in their state, thereby reducing rates. Also, lower income families will be eligible for government subsidies to help cover the cost of their premiums. The idea of the exchanges is where a change in access to healthcare is questionable. For lower income people, they will certainly have increased access to healthcare since they will receive money in the form of subsidies to help purchase insurance. But people who already have health insurance covereage through their employers may lose that insurance if their employer decides that it's cheaper and easier to put employees on the state exchange instead. Also, the mandate that requires businesses with at least 50 full time employees to offer insurance coverage may tempt some small businesses to reduce employee numbers or convert full time emplyees to part time to try to get around the mandate.
Just like any major new government program, Obamacare's full effects and costs will not be known until several years after it has been implemented. Only time will tell if the general access to health care has been increased.