How to make screen 'unsensitive' on incoming calls?
The way I solved the issue to my satisfaction was to buy and install the WidgetLocker Lockscreen app.  This is an awesome little app that basically allows you to replace your lockscreen (and incoming call screen too) with something customized.  I just have one horizontal slider to unlock the screen now, and it has completely eliminated accidental screen unlocks, as well as accidental accepts/rejects for incoming calls!  :-)

I would highly recommend WidgetLocker Lockscreen in any case, because being able to customize the lockscreen is really nice.