I think Andy has always played well against 'big' opponents and often lost to players well below him on the rankings. The difference in the last year is that he has started to show some consistency, and is beatng the people he should. Federer just looked like he couldn't be ars*d at times. Sometimes we all feel that way
I'd actually disagree with that. Ever since Andy joined tne tour, I'd say he has had a very good record at beating the players he should beat ( definitely compared to some who more often get unaccountably turned over by lower ranked opponents ).
What he is lately showing signs of, is beating these players more striaghtforwardly and with less use of energy than he used to.