Center Lock
I have an 05 Ltd V8 with full time four wheel drive (H4 and L4 positions). According to the manual, I should be able to depress the center differential lock button and go, however I have found that the indicator light continues to flash sometimes until I put the vehicle in reverse for a few feet. Once I do that, I'm good to go.
As far as snow traction goes, I've found H4, as is without using the center lock, is good to go, providing the best footing on a variety of surfaces.
With the recent snows in NoVA, I've played around with the center lock. I have to admit, it feels a little more "natural" with the vehicle stability control (VSC) turned off - with center lock engaged, which turns off the VSC, you can power slide the vehicle on snow; difficult if not impossible to do with the VSC on.
Try the reverse trick - I used to have to do it to lock the 4WD on my old Landcruiser and do it on my 4Runner, partly out of habit.
Good luck, Gordo