Hi D&O,
I think you overstate the discontent. On the left, he is increasingly seen as having done an immense job.
Saving the country from Bush's economic disaster. Done.
Stopping the inherited expansion of the deficit in real terms. Done.
Overseeing an increasing number of jobs. Done.
Recasting the healthcare system successfully. Done.
Avoiding new wars. Done.
Moving minority issues forwards. Done.
etc.
Obviously this may be challenged by his opponents, particularly in foreign policy terms (eg surrounding the mess in the Middle East), but he ain't a Republican. He was voted in to do Liberal things.
If the boorish portion of the discontent is crystallised in 20% of Republicans, it isn't all that alarming.