I just got mine back.
The sound as I'd describe it was similar to a geiger-counter - or - as just described, tapping fingernails against glass.
The weather didn't seem to stop it or make it louder.
As this has been the 3rd repair, GM/Cadillac customer service was informed also. The car spent 4 days at the dealer - not being touched cause the duffuses at GM were on 2-week holiday. Once the dealer 'talked' with tech support, they had me come back to the dealer, to help them figure out what the noise was. The dealer put in close to 3 hrs. Then, GM had the car sent to Webasto tech center, about an hr. from the dealer.
Webasto had the car just under 2 weeks, the work order wasn't complete when I picked up the car, but, here is a brief list of what was changed out. (Note: this was a mid-yr. build '04.)
a. Entire front glass
b. wind deflector - didn't get a good reason, other than they are making it different now.
c. sun shade - apparently there was a better one made, and currently being installed. (It does seem thicker than the 3mil thick pc of plastic/vinyl they use for the rear storage roll-up cover.)
d. insulation placed between headliner & metal where tracks are.
e. double sided tape
f. New reiforcement bars were added - apparently they weren't available for the '04's.
I'm waiting for the complete breakdown.
Driving home around town = so far no rattle. We'll see if this fix holds.
I'm still getting my pitcher of lemons ready..