I have a feeling the winner may come out of that top quater. There are some quality players there. Federer, Safin, Hewitt, Srichaphan, Ivanisevic (that's 3 former champions & one other Grand Slam winner along with a big name beater). Hewitt could play Goran in round 3 & Safin round 4, then Federer QF, that's a tough draw!
Grojean should get through the second quater, only Arthurs & Ferrero are the main challengers, perhaps Bjorkman.
Quarter 3 is strong aswell with Henman, Poo, Gonzalez, Hass, Blake & Nalbandien. Henman v Poo in round 4 shapes as the wouthwaterer there (if Poo can get past the frist round).
Roddick should have Quarter 4 all wrapped up, Schuttler, Rusedski & Enqvist the main contenders there.
So my semis would be:
Hewitt/Federer v Grojean
Henman/Poo v Roddick