I know and appreciate the fact that Logos wants and is working on providing mobile access to all resources, so consider this a supportive voice behind one particular resource: John Piper's Desiring God. Reading through it right now via the Kindle app on the iPad and I keep catching myself halfway in the act of tapping Bible passages and keep being surprised when tapping a footnote flips the page rather than gives it in a popup.
If for no other reason than the amount of Scripture Piper uses, having Desiring God in Logos on the iPad would be far superior to the Kindle version, making it easier to trace Piper's references while reading.