D3 liveview all the time at weddings. But never for any 'normal' shooting situation. I have used it for over the head, on the ground, macro of the rings (on tripod), on the tripod for groups, and also for getting spot on focus at small apertures.
best bet is to learn your gear and use whatever features you find help you the most and make it the easiest for you to capture the images you want.
At a recent wedding I could not shoot flash and was forced to shoot from the back of the church with a tele at ISO 1600 1/20 sec. AF was iffy due to the proportions and Live View was a life saver in terms of me being able to get a good focus. Multiple exposures allowed me to get a few good shots. Without Live View both Manual and AF would have been very difficult and unreliable. Live View is also great for things like macro work, astro work and much more. Its use in weddings is limited but when it's useful it's really useful.
