[Once again resurrecting this old thread as I finally got around to cracking mine open.]
First, getting it open and closed again was easy, there wasn't any of the sealing I expected. It also doesn't look like the circuit board is well coated so I wouldn't expect it to last outside very long in harsh environments.
There were a few things I didn't notice in George's pictures, though now that I know they are there I can see them.
First, for anyone who is interested in some electronics hacking: there are pads with nice open holes for the SPI bus next to the AS3935 lightning sensor chip. Maybe this winter I'll hook it up to a logic analyzer and/or see if I can setup an RPi as a recorder to get a better handle on how this whole thing is working. I also noticed a nice "reset" pad near the covered blob that is likely the Acurite MCU. So I'm guessing it is possible to use that to temporarily or semi-permanently disabled the Acurite MCU if you were interested in experimenting with the AS3935.
Second, antennas an orientation. On the backside of the PCB, towards the back of the case there is a small white-ish "PCB" antenna attached for the lightning sensor. I believe someone noted in one of the threads the best orientation for this sensor is with it's back towards what ever direct storms most typically approach from. Since this is behind the main PCB, this make some sense. The antenna is somewhat near the holes in the front of the case near the red panel.
(There is also an inductor that can been seen in George's photo of the chip numbers. It looks like a little tiny am bar antenna. It's labeled L1, but is on the front side of the PCB. This might just be for loading and might not be used as part of the sensor's antenna.)