I've occasionally had the same issue ending a call with the external touch pad. Usually end up flipping the phone open and using the hard key. As nice as the touch sensitive pad looks indoors, I might have preferred a 'conventional' one, especially in bright sunlight when it's difficult to see either it or the display.
Haven't had the illumination delay problem though.
Well, I have now had this phone for two months and I have noticed some other problems with it. The other night, I was looking at the contacts on the external display and the phone froze. When I flipped open the phone to see if it was still on, I found that it wasn't and it had rebooted all by itself. I have no idea why that happened. I did a battery pull on the phone twice (with the device on) and it seems to be working okay now. If it keeps freezing on me, I might get a different phone.