Just updated our version of NGUI to 3.5.4, and got a single compile error. UILabelInspector, line 195.
It appears that GUILayoutEditor.GetControlRect() is not exposed in Unity 4.2.
I've encircled this w/ #if/#endif statements in our code, but it would probably be a good idea to prevent it in the source.
We won't be upgrading Unity because we're too close to shipping, but the NGUI updates fixed a lot of problems for us.
Thanks