I want to say that it was at least two hours if not 3 before my phone came on from a total discharge.
The phone would vibrate and flash if I plugged or unplugged etc... I played with it enough that it came on was still pretty much dead on the charge but once on and plugged in it actually charged so what I read above that it won't charge if its not on seems to hold true.
Of course that was all before the update.
HTC One X (original from AT&T)
Asus Transformer Infinity TF700T
Asus Transformer Prime TF201 - Now in my daughtes hands
Former Devices: Nokia Lumia 900, Samsung Focus, Dell Venue Pro (for 2 weeks), Tilt 2, Fuze, Tilt, HP HX4700