The All Just a Dream ending is interpreted by the audience in different ways...
Kevin chooses to throw the case, trading his skill at being a lawyer for being a better man. But Milton is still lurking around and will attempt to tempt him yet again.
Another interpretation is that Eveyything did happen, but was undone. Milton reverted time back to the point before Kevin's career-defining case in order to keep trying alternate pathways until he can get to the point where Kevin submits. There's the implication that Milton will do this as many times as necessary until he wins.
I removed this Audience Reactions example from the main page, but I'm not sure what Audience Reactions or YMMV category it would fall under.