I am delighted to read that two better known Australian sparkler
producers - Chandon Austalia and Seppelt - have switched to crown
caps for their top wines:

http://www.wineoftheweek.com/murray/0404chandon.html

I especially like the slip label around the crown cap down the
neck reading

CROWN SEAL CLOSURE
RECOMMENDEND SEAL FOR LONG
TERM BOTTLE MATURATION

Especially the fact that Chandon has moved to this step could be a
giant step to cork-taint-free sparklers worldwide.

M.