I think he wasn't ambitious enough and was too keen on consensus.* He wasted his first year trying to reach agreement with the Republicans when they had sworn not to allow him any policy success. His initial health reforms were rebuffed, not just by Republicans, and he ended up with a monstrous health plan with all sorts of sweeteners for special interests. But this was not the plan he put forward, it was just the best he could get through. It is telling that it was still an improvement on the existing system.
Despite the scare stories and anecdotal stories, a lot of people who had poor or no health insurance have benefited from the plan and many of the poor are southern Republicans (think one huge Clacton). It will be almost impossible to reverse the health plans and if they succeed the Republicans will alienate yet another group of supporters.
* The wasted first year defined his presidency. He should have done what Gingrich did with the Contract with America and pushed as much as possible in the first 100 days. That was when he could have made his mark. Instead his only domestic legacy is the healthcare hodge-podge and his only international legacy is ... well, we are still waiting on that. His main claim to fame is that he is not George W Bush or someone like him. This he achieved and that won him the Nobel prize.
He often does make decisions, but in his own time. This makes him look like he is dithering. Then when he has evaluated the situation and made a decision he is rather lost in making it happen, partly because of Republican obstruction and partly because he just leaves policy implementation to others. He makes the decision, makes a nice speech, and then disconnects from the process.
The end result is a poor presidency with little achievement, but it is not a disastrous presidency like that of Bush.
