Richard Olszewski wrote a review of Deuter Sun Roof & Rain Cover on May 18, 2012
Not ventilated well enough for sunny days... which is, of course, when you would use it. Hot air rises, so it needs ventilation in the top.
The rain cover is zipped inside for inconvenient access... a sudden rain will render it useless, as will a heavy rain; it only covers the top open part of the back pack.
And the final non-feature, my personal favorite, there is no place to store it... so you will eventually misplace it - which is, of course, what my daughter did on her FIRST overnight camping trip... an expensive lesson.