This shoot for Usher's OMG tour was hugely bright, so much so that you could probably shoot this tour with a kit lens. However, that bright light didn't go to waste, because it was very useful for keeping shutter speeds high during this kinetic set.
This show actually reminded me in some ways of No Doubt's epic 2009 tour, with the abundant white light, high energy, and non-stop action. Leaving the pit after photographing Usher, I felt like this was easily one of the top 5 most fun sets to shoot of the year.
During the second song, Usher goes to the back of the stage and performs on a platform for about half of the number, so bring a telephoto.
Even with a telephoto (I used the Nikon 70-200mm f/2.8), the shooting opportunities are relatively limited, so feel free to take that opportunity to change lenses if you like before he comes back to the front of the stage.