I have one problem with the new behaviour, but first of all - the new inspector rocks. Huge improvements. Awesome.
Just one thing - with the new behaviour, when you enter or change values of fields, the inspector applies the changes while you are typing, and not when you press enter or move to another field.
This is very nice usually, but when you are trying to change values like the near clip plane of the camera from 0.3 to 0.1 during play, once you erase that 3- Unity uses 0 as the value, displays some error message in the console and hangs in an infinite loop.
The new behaviour is not to blame here for the freeze, and on 99% percent of the time I rather enjoy seeing changes on the fly without having to move between the fields to re-edit values.
But it might be nice to have a place in the preferences (or a button on the inspector itself) where we could maybe toggle this feature on and off.