You get an amazing bird's eye view of the stages. I'd recommend the morning, as there's no much going on yet, there are DJs and other bands performing up there and the air feels especially nice, but I guess that it'd be even more interesting at dusk or after dark, as the lights from the stages would be even more powerful. Either way, it's worth it. Try going on Saturday/Sunday and listen as the din of the speakers below slowly washes away as you ascend.

Jinki

*Photo taken by Sam and used with permission from '05 Fuji Rock Express