The Republicans have painted themselves into a corner. They know that once Obamacare is implemented, people will like it. More people will have health coverage. You won’t have to change insurance companies (and often doctors) when you change jobs, and will be able to get health insurance even if you quit your job to start a company. Even before it is fully implemented, insurance premiums are going down and coverage is going up.
The main people who lose are the health insurance companies, and the politicians who receive campaign donations from them. Which might explain why the Republicans are so dead set against it that they are threatening to shut down the government.