Siddle has loads of aggression and his seamers will only get better, Hilf is the best swing bowler in Australia, and his tight bowling allowed johnson and siddle to attack from the other end.
mcdonald is no mug but Hilf and siddle stayers...Lee and Clark will have a tough job getting back in
Like you mention, it's the balance of the attack I liked. Johnson and Siddle can pepper the batsmen because they know Hilfy and McDonald were able to restrict the run rate at the other end. That's why we ultimately picked Hauritz for a couple of Tests as the spinner, since Krejza couldn't stop the scoring. An attack full of wicket taking, aggressive bowlers may not be as effective without a relatively conservative, run stopping bowler.
Of course the great advantage of Hilfy is that if there is any swing he can exploit it, and that makes him a potentially dangerous containing bowler a la Glenn McGrath. All teams want those. However, I don't know whether Hilfy will be quite as economical is less favourable conditions.
Still I guess Stuart Clark is another viable alternative for the holding role and Nathan Bracken would also do it quite well too. Lee is more an aggressor so he might be competing with Siddle for a spot.
This is the great advantage of playing new players and seeing them do well, suddenly Australia has heaps of decent/good quicks: Lee, Clark, Johnson, Siddle, Hilfenhaus, Bollinger, Tait, Bracken. McDonald and Watson have shown they can do a good job with the ball too.
