The main changes to the system for those with insurance are that:
1) It will be illegal for insurance companies to deny you coverage due to a preexisting condition.
2) It will be against the law for insurance companies to drop your coverage when you get sick, or water it down.
3) No more cap on the amount you can claim in a given year, or even lifetime.
4) Companies will have to pay out for routine checks to catch serious illnesses before they take hold.
For those without:
1) Those without insurance will be offered low cost cover from a Market where competition will keep prices low.
2) Those with long term medical conditions will be provided with cover to keep them away from financial ruin (One of McCain's campaign proposals)
From listening to Obama's speech to Congress it would seem that the main aim for this plan is to stop insurance companies from exploiting people. It would lower the cost of insurance and increase the cover available to people who need it.
In return to those who claim the Plan would push America into more debt and destroy them economically, Obama Claims he will not sign a Bill which puts anymore pressure on the taxpayer or that will add to their deficit. This claim is backed up by a clause which assures that cuts will be made if savings are not produced. Obama goes on to criticise the current system for it's waste and for expenses that don't improve people's health.
I'm really struggling to see why the 'right' supporters are so concerned. It doesn't seem to be anywhere near as socialist as their making. The criticisms seem to be a last grasp hope of preserving an individualist America