The trouble I've found with theme selection is that you get (x) with one and (y) with another: e.g., I like Twenty 11 for that possibility but I do't like the way it houses Comments; and I like Coraline for the way it houses Comments but I don't like that you can't change links colours, and so on. You could spend the rest of your days trying one theme after another in search of the perfect combo; but your readers would get pretty irritable. I reckon that every theme coming out should be accompanied by a complete list of attributes: how helpful would that be?!
Well. Mebbe custom design will bring with it other goodies I hadn't thought of, eh?