This checklist is straight forward but it leaves out one critical step and a few other important steps as well. There are few things in this airplane that can kill you, but this is one of them. If you are highly trained Gulfstream pilot none of these will be problems because you've known about them since the G-II and have habit patterns to keep you safe. If you aren't a highly trained Gulfstream pilot or are flying with a newbee, read on.
Everything here is from the G-450 Aircraft Flight Manual, with a few comments in blue.
[G-450 Aircraft Flight Manual §2-05-50]
Figure: Flight Controls Synoptic, from FSI G450 Pilot Training Manual Vol 2, Figure 14-10.
Repeat after me: "Three green, four in the air." This is critical. You don't want to move to the next step in the checklist until you've ensured all four WOWs are in the air mode.
Why? See G450 Abnormal Procedures / WOW Fail for an explanation of why and Mishaps / GV N777TY for a description of what can happen if you skip this step. Note also that Gulfstream now says the three green lights in the gear handle take priority over what you see in the synoptic. (The three green lights in the gear handle panel are wired directly, the synoptic uses the same switches but they are reported through the MAUs.)
The switch light should be illuminated. If you miss this step, your first indication will be the aircraft will not plant itself once the main gear have touched down and the second step will be a sense that braking isn't as good as it usually is.
Make sure you have the brakes page displayed someplace where both pilots can see it. If you have an Anti-skid Failure or a malfunction requiring Braking Using Emergency Brake, you will need this page in view. You should also take a quick look at the hydraulics synoptics to ensure you have 3000 psi and adequate quantity in both systems.
I don't wait for the actual speed, I just note the correct speed is bugged. The correct speed should be VREF plus half the steady state wind plus half the gust, but the additive must be at least 5 knots and no more than 20 knots.
Some operators intentionally skip this step, reasoning they want to know if they are having any issues. I select INHIBIT because the book tells me too. But I am on the fence about the technique.
FSI G-450 PTM, FlightSafety Internation Gulfstream G450 Pilot Training Manual, Volume 2, Aircraft Systems, October 2008
Gulfstream G450 Airplane Flight Manual, Revision 35, April 18, 2013