[nGenLight]

Don't 1/2 rax expo on maps with wide naturals, because the consensus between many of us higher level Protoss players is that a 3gate pressure into 6 gate push outright kills this.

As TADeth once put it the best "1 rax expand into... lose".

There are two styles which I find the most troubling:
(1) oGsSuperNova's mech/bio style.
BO: Techlab Marauder opener, In-Base CC, Seige tank expand, Techlab Starport makes a Raven and a Banshee(Don't ever let this die, fear of the banshee) before switching to a reactor make Medivacs, add on multiple barracks, transition into mass MMM/Tank/Raven off 2 saturated(w/mule) base and deny Protoss third.
(2) MMA/QXC/Select Bio/Heavy drop harrass style.
BO: 2 Rax, Reactor+Techlab, In-Base CC, Reactor Starport, start map controlling off multi-pronged attacks/drops and outexpand the Protoss.