The choices are easier than they were with Vista. For Home users I’d recommend Home Premium due to the inclusion of Media Center (once you’ve played with this you’ll see why).
For Business – I’m torn between Professional and Ultimate. One of the features in Ultimate which I’m keen to play with for businesses is “Direct Access”. I’m surprised this isn’t included in the Business edition – as it’s clearly aimed as a business feature? I’ll write another post once I’ve evaluated this feature against a 2008 R2 Server.