Full disclaimer: My play experience with 5e is somewhat limited-- about 3 levels as a variant human life cleric, 2 levels as a variant human fighter, 1 level as a stout halfling rogue.
Class Balance: I have heard that some classes and subclasses are clearly mechanically inferior to others; but I have really enjoyed all three that I have played, and no one of them has seemed markedly better or worse than any other.
Backgrounds: Backgrounds can lead to a pretty varied feel between different types of characters. My cleric, for example, had the soldier background; and she felt very different from my fighter who had the criminal background; who felt very different from my rogue who had the outlander background (representing the fact that she had been exiled from her village). It reminds me-- in a good way-- of Iron Kingdoms-- which has three very general classes, but lets youc ouple them with two backgrounds/careers. I think I actually prefer the IK way of doing things, but it would have represented too radical of a departure from what we all know and love as D&D.