Second, this is not a trip for solitude. Many, many people hike this canyon each day and the take-out is at Sinawava. (Valerie called it the back-door to Disneyworld.) Let's just say that one is less likely to be trampled at a Who concert. This is a very unpleasant feature of Zion National Park and summers there are to be avoided.
All that being said, this is one of the most beautiful trips I have ever done. The walls are soaring, the flora is verdant, the river is refreshing. The hiking is never boring. Around every corner is a sight more beautiful than the last. The six or eight miles from the mouth of Deep Creek down to Orderville Canyon are spectacular. This is a place that one must see to believe. If you get the opportunity, and you are modestly fit and not too whiny--at least no whinier than I am--you have got to do this hike.