N9 is missing the N900's kickstand.
N9 is midding the N900's lens cover.
N9 is missing the N900's Qwerty physical keyboard
N9 is missing the more precice Resistive touchscreen which can be used by those wearinging motorcycle gloves or winter gloves. Imagie trying to edit GPS destinations on with a capacitive screen... You need to look at your mirrors for a hole in heavy traffic, grab your clutch as you let your throttle go, downshift, move over to the side of the road and while watching your mirrors for out of control idtiots entering the breakdown lane and freight trucks losing control, take you glove off so you can use your phone's screen.... while holding the clutch in to keep yourself in 1st gear so you can get out of the way fast if trouble shows up in your mirror...
If I'm going to a capacitive screen I'm going to the Asus Transformer, using Skype for calls... if only a 3G or 4G version were available and I could port my AT&T number to Skype... I don't know where I'll be going after the N900, but it won't be the N9.
Most of all if Elop continues to turn Nokia into a pile of stupid (let us be honest, of all the choices Windows Phone is the least viable) I'll be moving to Asus-Android.